# FETCHMAIL

Date:
  2025-10-10

## NAME

fetchmail - fetch mail from a POP, IMAP, ETRN, or ODMR-capable server

## SYNOPSIS

fetchmail [option...] [mailserver...]
fetchmailconf

## DESCRIPTION

fetchmail is a mail-retrieval and forwarding utility; it fetches mail from remote mail servers and forwards it to your local (client) machine's delivery system. You can then handle the retrieved mail using normal mail user agents such as mutt(1), elm(1) or Mail(1). The fetchmail utility can be run in a daemon mode to repeatedly poll one or more systems at a specified interval.

The fetchmail program can gather mail from servers supporting any of the common mail-retrieval protocols: POP2 (legacy, to be removed from future release), POP3, IMAP2bis, IMAP4, and IMAP4rev1. It can also use the ESMTP ETRN extension and ODMR. (The RFCs describing all these protocols are listed at the end of this manual page.)

While fetchmail is primarily intended to be used over on-demand TCP/IP links (such as SLIP or PPP connections), it may also be useful as a message transfer agent for sites which refuse for security reasons to permit (sender-initiated) SMTP transactions with sendmail.

## DEPRECATION AND CRYPTOGRAPHIC SECURITY WARNINGS

Several cryptographic algorithms that are referenced by mail standareds for authentication were based on MD4 or MD5 or SHA1 algorithms that were developed in 1990, 1991 and 1995 respectively. 30 years later, these are no longer deemed secure, and are considered broken.

Not all IETF standards and RFCs have given up on them, and some protocols actively require something that incorporates MD4, MD5 or SHA1 in some form so disabling their use in fetchmail altogether would also pull the plug on, say, protocols such as ODMR, or formerly-popular authentication schemes such as POP3 with APOP.

The recommendation is to prefer TLS-wrapped connections via dedicated ports 993 (IMAP4) or 995 (POP3) or STARTTLS in-band negotiation with such authentication schemes, to reduce the risk to expose login credentials.

Also, weak authentication schemes will be phased out from future fetchmail releases, please see the NEWS file that should have come with your distribution of fetchmail.

## SUPPORT, TROUBLESHOOTING

For troubleshooting, tracing and debugging, you need to increase fetchmail's verbosity to actually see what happens. To do that, please run both of the two following commands, adding all of the options you'd normally use.

    env LC_ALL=C fetchmail -V -v --nodetach --nosyslog

> (This command line prints in English how fetchmail understands your configuration.)

    env LC_ALL=C fetchmail -vvv  --nodetach --nosyslog

> (This command line actually runs fetchmail with verbose English output.)

Also see item #G3 in fetchmail's FAQ.

You can omit the LC_ALL=C part above if you want output in the local language (if supported). However if you are posting to mailing lists, please leave it in. The maintainers do not necessarily understand your language, please use English.

### QUICKSTART

1. Set up a local SMTP mail server, or command-line based mail delivery agent such as maildrop or dovecot-lda, configure and test and debug it. Make sure that mail you deliver to yourself through it ends up in the right place. Do NOT continue unless and until this works or you risk losing mail!

2. Create a .fetchmailrc file in your home directory that looks roughly like this, for POP3 fetches.

    poll mailserver.example.org proto POP3 uidl
    user joe.sixpack
    keep ssl

You need to adjust several elements here: mailserver.example.org is the server's name. joe.sixpack is the login name to use for the server. keep states that messages should be left on the server, rather than deleted. ssl states that the connection should be encrypted. If you need to use IMAP instead of POP3, change "proto POP3 uidl" to "proto IMAP".

If you chose to deliver through a command-line program, add an mda option, for instance:

    mda "/usr/bin/maildrop -d %T"

3. And then make sure the ~/.fetchmailrc file is not readable or writable to anyone but yourself:

    chmod 0600 ~/.fetchmailrc

4. Finally, run fetchmail in verbose mode and see that it works. To limit impact, if something goes wrong, we just try two messages:

    fetchmail -v --fetchlimit 2

If then the POP3 server refuses UIDL, you cannot use the "keep" option on that server and you need to remove the uidl and keep options, but note that then fetchmail will remove messages it has successfully delivered from the server.

## TLS (SSL) QUICKSTART

Your fetchmail distribution should have come with a README.SSL file, which see. It is recommended to configure all polls with --ssl --sslproto tls1.2+ if supported by the server, which configures fetchmail along recent IETF proposed standards and best current practices, RFC-8314, RFC-8996, RFC-8997.

Fetchmail 6.6.0 and newer also support TLS and STARTTLS for SMTP, see the --smtphost option for how to configure those.

## CONCEPTS

If fetchmail is used with a POP or an IMAP server (but not with ETRN or ODMR), it has two fundamental modes of operation for each user account from which it retrieves mail: singledrop- and multidrop-mode.

In singledrop-mode,

  fetchmail assumes that all messages in the user's account (mailbox) are intended for a single recipient. The identity of the recipient will either default to the local user currently executing fetchmail, or will need to be explicitly specified in the configuration file.

  fetchmail uses singledrop-mode when the fetchmailrc configuration contains at most a single local user specification for a given server account.

In multidrop-mode,

  fetchmail assumes that the mail server account actually contains mail intended for any number of different recipients. Therefore, fetchmail must attempt to deduce the proper "envelope recipient" from the mail headers of each message. In this mode of operation, fetchmail almost resembles a mail transfer agent (MTA).

  Note that neither the POP nor IMAP protocols were intended for use in this fashion, and hence envelope information is often not directly available. The ISP must store the envelope information in some message header and. The ISP must also store one copy of the message per recipient. If either of the conditions is not fulfilled, this process is unreliable, because fetchmail must then resort to guessing the true envelope recipient(s) of a message. This usually fails for mailing list messages and Bcc:d mail, or mail for multiple recipients in your domain.

  fetchmail uses multidrop-mode when more than one local user and/or a wildcard is specified for a particular server account in the configuration file.

In ETRN and ODMR modes,

  these considerations do not apply, as these protocols are based on SMTP, which provides explicit envelope recipient information. These protocols always support multiple recipients.

As each message is retrieved, fetchmail normally delivers it via SMTP to port 25 on the machine it is running on (localhost), just as though it were being passed in over a normal TCP/IP link. fetchmail provides the SMTP server with an envelope recipient derived in the manner described previously. The mail will then be delivered according to your MTA's rules (the Mail Transfer Agent is usually sendmail(8), exim(8), or postfix(8)). Invoking your system's MDA (Mail Delivery Agent) is the duty of your MTA. All the delivery-control mechanisms (such as .forward files) normally available through your system MTA and local delivery agents will therefore be applied as usual.

If your fetchmail configuration sets a local MDA (see the --mda option), it will be used directly instead of talking SMTP to port 25.

If the program fetchmailconf is available, it will assist you in setting up and editing a fetchmailrc configuration. It runs under the X window system and requires that the language Python and the Tk toolkit (with Python bindings) be present on your system. If you are first setting up fetchmail for single-user mode, it is recommended that you use Novice mode. Expert mode provides complete control of fetchmail configuration, including the multidrop features. In either case, the 'Autoprobe' button will tell you the most capable protocol a given mail server supports, and warn you of potential problems with that server.

## PREFACE ON THIS MANUAL

Fetchmail's run-time strings have been translated (localized) to some languages, but the manual is only available in English. In some situations, for comparing output to manual, it may be helpful to switch fetchmail to English output by overriding the locale variables, for instance:

    env LC_ALL=C fetchmail # add other options before the hash

    env LANG=en fetchmail # other options before the hash

or similar. Details vary by operating system.

## GENERAL OPERATION

The behavior of fetchmail is controlled by command-line options and a run control file, ~/.fetchmailrc, the syntax of which we describe in a later section (this file is what the fetchmailconf program edits). Command-line options override ~/.fetchmailrc declarations.

Each server name that you specify following the options on the command line will be queried. If you do not specify any servers on the command line, each 'poll' entry in your ~/.fetchmailrc file will be queried, unless the idle option is used, which see.

To facilitate the use of fetchmail in scripts and pipelines, it returns an appropriate exit code upon termination -- see EXIT CODES below.

The following options modify the behavior of fetchmail. It is seldom necessary to specify any of these once you have a working .fetchmailrc file set up.

Almost all options have a corresponding keyword which can be used to declare them in a .fetchmailrc file.

Some special options are not covered here, but are documented instead in sections on AUTHENTICATION and DAEMON MODE which follow.

### General Options

-? | --help

  Displays option help.

-V | --version

  Displays the version information for your copy of fetchmail. No mail fetch is performed. Instead, for each server specified, all the option information that would be computed if fetchmail were connecting to that server is displayed. Any non-printable characters in passwords or other string names are shown as back-slashed C-like escape sequences. This option is useful for verifying that your options are set the way you want them.

-c | --check

  Return a status code to indicate whether there is mail waiting, without actually fetching or deleting mail (see EXIT CODES below). This option turns off daemon mode (in which it would be useless). It does not play well with queries to multiple sites, and does not work with ETRN or ODMR. It will return a false positive if you leave read but undeleted mail in your server mailbox and your fetch protocol cannot tell kept messages from new ones. This means it will work with IMAP, not work with POP2, and may occasionally flake out under POP3.

-s | --silent

  Silent mode. Suppresses all progress/status messages that are normally echoed to standard output during a fetch (but does not suppress actual error messages). The --verbose option overrides this.

-v | --verbose

  Verbose mode. All control messages passed between fetchmail and the mail server are echoed to stdout. Overrides --silent. Doubling this option (-v -v) causes extra diagnostic information to be printed.

--nosoftbounce
  (since v6.3.10, Keyword: set no softbounce, since v6.3.10)
  Hard bounce mode. All permanent delivery errors cause messages to be deleted from the upstream server, see "no softbounce" below.
--softbounce
  (since v6.3.10, Keyword: set softbounce, since v6.3.10)
  Soft bounce mode. All permanent delivery errors cause messages to be left on the upstream server if the protocol supports that. This option is on by default to match historic fetchmail documentation, and will be changed to hard bounce mode in the next fetchmail release.

### Disposal Options

-a | --all | (since v6.3.3) --fetchall
  (Keyword: fetchall, since v3.0)
  Retrieve both old (seen) and new messages from the mail server. The default is to fetch only messages the server has not marked seen. Under POP3, this option also forces the use of RETR rather than TOP. Note that POP2 retrieval behaves as though --all is always on (see RETRIEVAL FAILURE MODES below) and this option does not work with ETRN or ODMR. While the -a and --all command-line and fetchall rcfile options have been supported for a long time, the --fetchall command-line option was added in v6.3.3.
-k | --keep
  (Keyword: keep)
  Keep retrieved messages on the remote mail server. Normally, messages are deleted from the folder on the mail server after they have been retrieved. Specifying the keep option causes retrieved messages to remain in your folder on the mail server. This option does not work with ETRN or ODMR. If used with POP3, it is recommended to also specify the --uidl option or uidl keyword.
-K | --nokeep
  (Keyword: nokeep)
  Delete retrieved messages from the remote mail server. This option forces retrieved mail to be deleted. It may be useful if you have specified a default of keep in your .fetchmailrc. This option is forced on with ETRN and ODMR.
--moveto <folder>
  (Keyword: moveto)
  In IMAP mode, instead of flushing a message, move it to the given IMAP folder instead. This is useful for avoiding data loss while testing, and is the preferred way to delete emails on certain implementations, for example Google wants you to delete mails by moving them to [Gmail]/Trash. Only available for IMAP servers. This option is only accepted with --proto imap, but not if IMAP is chosen automatically. It is ineffective when --keep is in effect.
-F | --flush
  (Keyword: flush)
  POP3/IMAP only. This is a dangerous option and can cause mail loss when used improperly. It deletes old (seen) messages from the mail server before retrieving new messages. Warning: This can cause mail loss if you check your mail with other clients than fetchmail, and cause fetchmail to delete a message it had never fetched before. It can also cause mail loss if the mail server marks the message seen after retrieval (IMAP2 servers). You should probably not use this option in your configuration file. If you use it with POP3, you must use the 'uidl' option. What you probably want is the default setting: if you do not specify '-k', then fetchmail will automatically delete messages after successful delivery.
--limitflush

  POP3/IMAP only, since version 6.3.0. Delete oversized messages from the mail server before retrieving new messages. The size limit should be separately specified with the --limit option. This option does not work with ETRN or ODMR.

### Protocol and Query Options

-p <proto> | --proto <proto> | --protocol <proto>
  (Keyword: proto[col])
  Specify the protocol to use when communicating with the remote mail server. If no protocol is specified, the default is AUTO. proto may be one of the following:
  AUTO

    Tries IMAP, POP3, and POP2 (skipping any of these for which support has not been compiled in).

  POP2

    Post Office Protocol 2 (legacy, to be removed from future release)

  POP3

    Post Office Protocol 3

  APOP

    Use POP3 with old-fashioned MD5-challenge authentication. Considered not resistant to man-in-the-middle attacks.

  RPOP

    Use POP3 with RPOP authentication.

  KPOP

    Use POP3 with Kerberos V4 authentication on port 1109.

  SDPS

    Use POP3 with Demon Internet's SDPS extensions.

  IMAP

    IMAP2bis, IMAP4, or IMAP4rev1 (fetchmail automatically detects their capabilities).

  ETRN

    Use the ESMTP ETRN option.

  ODMR

    Use the On-Demand Mail Relay ESMTP profile.

All these alternatives work in basically the same way (communicating with standard server daemons to fetch mail already delivered to a mailbox on the server) except ETRN and ODMR. The ETRN mode allows you to ask a compliant ESMTP server (such as BSD sendmail at release 8.8.0 or higher) to immediately open a sender-SMTP connection to your client machine and begin forwarding any items addressed to your client machine in the server's queue of undelivered mail. The ODMR mode requires an ODMR-capable server and works similarly to ETRN, except that it does not require the client machine to have a static DNS.

-U | --uidl
  (Keyword: uidl)
  Force UIDL use (effective only with POP3). Force client-side tracking of 'newness' of messages (UIDL stands for "unique ID listing" and is described in RFC1939). Use with 'keep' to use a mailbox as a baby news drop for a group of users. The fact that seen messages are skipped is logged, unless error logging is done through syslog while running in daemon mode. Note that fetchmail may automatically enable this option depending on upstream server capabilities. Note also that this option may be removed and forced enabled in a future fetchmail version. See also: --idfile.
--idle (since 6.3.3)
  (Keyword: idle, since before 6.0.0)
  Enable IDLE use (effective only with IMAP). Note that this works with only one account and one folder at a given time, other folders or accounts will not be polled when idle is in effect! While the idle rcfile keyword had been supported for a long time, the --idle command-line option was added in version 6.3.3. IDLE use means that fetchmail tells the IMAP server to send notice of new messages, so they can be retrieved sooner than would be possible with regular polls. Fetchmail also contains a workaround to emulate IDLE; this workaround was ineffective since 6.4.22 and fixed in 6.5.3 (broken by commit 616e8c70 and repaired in f91923b5), Gitlab issue #69.
--forceidle (since 6.5.0)
  (Keyword: forceidle, since 6.5.0)
  Use IDLE even if the server does not advertise it in its capabilities. This is a dangerous option, use carefully.
--idletimeout (since 6.5.0)
  (Keyword: idletimeout, since 6.5.0)
  Set the timeout (in seconds) for the IDLE command because too many servers break the protocol (which requires 30 minutes) and hang up after a few minutes. Default value: 1680 s (= 28 min).
-P <portnumber> | --service <servicename>
  (Keyword: service) Since version 6.3.0.
  The service option permits you to specify a service name to connect to. You can specify a decimal port number here, if your services database lacks the required service-port assignments. See the FAQ item R12 and the --ssl documentation for details. This replaces the older --port option.

Note that this does not magically switch between TLS-wrapped and STARTTLS modes, if you specify a port number or service name here that is TLS-wrapped, meaning it starts to negotiate TLS before sending application data in the clear, you may need to specify --ssl on the command line or ssl in your rcfile.

--port <portnumber>
  (Keyword: port)
  Obsolete version of --service that does not take service names. Note: this option may be removed from a future version.
--principal <principal>
  (Keyword: principal)
  The principal option permits you to specify a service principal for mutual authentication. This is applicable to POP3 or IMAP with Kerberos 4 authentication only. It does not apply to Kerberos 5 or GSSAPI. This option may be removed in a future fetchmail version.
-t <seconds> | --timeout <seconds>
  (Keyword: timeout)
  The timeout option allows you to set a server-non-response timeout in seconds. If a mail server does not send a greeting message or respond to commands for the given number of seconds, fetchmail will drop the connection to it. Without such a timeout fetchmail might hang until the TCP connection times out, trying to fetch mail from a down host, which may be very long. This would be particularly annoying for a fetchmail running in the background. There is a default timeout which fetchmail -V will report. If a given connection receives too many timeouts in succession, fetchmail will consider it wedged and stop retrying. The calling user will be notified by email if this happens.

  Beginning with fetchmail 6.3.10, the SMTP client uses the recommended minimum timeouts from RFC-5321 while waiting for the SMTP/LMTP server it is talking to. You can raise the timeouts even more, but you cannot shorten them. This is to avoid a painful situation where fetchmail has been configured with a short timeout (a minute or less), ships a long message (many MBytes) to the local MTA, which then takes longer than timeout to respond "OK", which it eventually will; that would mean the mail gets delivered properly, but fetchmail cannot notice it and will thus re-fetch this big message over and over again.

--plugin <command>
  (Keyword: plugin)
  The plugin option allows you to use an external program to establish the TCP connection. This is useful if you want to use ssh, or need some special firewall setup. The program will be looked up in $PATH and can optionally be passed the host name and port as arguments using "%h" and "%p" respectively (note that the interpolation logic is rather primitive, and these tokens must be bounded by whitespace or beginning of string or end of string). Fetchmail will write to the plugin's stdin and read from the plugin's stdout.
--plugout <command>
  (Keyword: plugout)
  Identical to the plugin option above, but this one is used for the SMTP connections.
-r <name> | --folder <name>
  (Keyword: folder[s])
  Causes a specified non-default mail folder on the mail server (or comma-separated list of folders) to be retrieved. The syntax of the folder name is server-dependent. This option is not available under POP3, ETRN, or ODMR.
--tracepolls
  (Keyword: tracepolls)
  Tell fetchmail to poll trace information in the form 'polling account %s' and 'folder %s' to the Received line it generates, where the %s parts are replaced by the user's remote name, the poll label, and the folder (mailbox) where available (the Received header also normally includes the server's true name). This can be used to facilitate mail filtering based on the account it is being received from. The folder information is written only since version 6.3.4.
--ssl
  (Keyword: ssl)
  Causes the connection to the mail server to be encrypted via SSL, by negotiating SSL directly after connecting (called SSL-wrapped mode, or Implicit TLS by RFC-8314). Please see the description of --sslproto below! More information is available in the README.SSL file that ships with fetchmail.

  Note that even if this option is omitted, fetchmail may still negotiate SSL in-band for POP3 or IMAP, through the STLS or STARTTLS feature. You can use the --sslproto option to modify that behavior.

  If no port is specified, the connection is attempted to the well known port of the SSL version of the base protocol. This is generally a different port than the port used by the base protocol. For IMAP, this is port 143 for the clear protocol and port 993 for the SSL secured protocol; for POP3, it is port 110 for the clear text and port 995 for the encrypted variant.

  If your system lacks the corresponding entries from /etc/services, see the --service option and specify the numeric port number as given in the previous paragraph (unless your ISP had directed you to different ports, which is uncommon however).

--nossl
  (Keyword: nossl)
  Cancels out a default of ssl given earlier, in defaults, or in an rcfile if --nossl is given on the command-line. Use --sslproto with proper argument to enable STARTTLS.
--sslcert <name>
  (Keyword: sslcert)
  For certificate-based client authentication. Some SSL encrypted servers require client side keys and certificates for authentication. In most cases, this is optional. This specifies the location of the public key certificate to be presented to the server at the time the SSL session is established. It is not required (but may be provided) if the server does not require it. It may be the same file as the private key (combined key and certificate file) but this is not recommended. Also see --sslkey below.

NOTE: If you use client authentication, the user name is fetched from the certificate's CommonName and overrides the name set with --user.

--sslkey <name>
  (Keyword: sslkey)
  Specifies the file name of the client side private SSL key. Some SSL encrypted servers require client side keys and certificates for authentication. In most cases, this is optional. This specifies the location of the private key used to sign transactions with the server at the time the SSL session is established. It is not required (but may be provided) if the server does not require it. It may be the same file as the public key (combined key and certificate file) but this is not recommended.

  If a password is required to unlock the key, it will be prompted for at the time just prior to establishing the session to the server. This can cause some complications in daemon mode.

  Also see --sslcert above.

--sslproto <value>
  (Keyword: sslproto, NOTE: semantic changes since v6.4.0)
  This option has a dual use, out of historic fetchmail behaviour. It controls both the SSL/TLS protocol version and, if --ssl is not specified, the STARTTLS behaviour (upgrading the protocol to an SSL or TLS connection in-band). Some other options may however make TLS mandatory -- in particular, --sslcertck is now default behavior and requires SSL.

  Recognized values for --sslproto are given below. You should normally choose one of the auto-negotiating options, i. e. 'tls1.2+' or 'auto' or one of the other options ending in a plus (+) character. Note that depending on the TLS library (OpenSSL, AWS-LC, wolfSSL) version and configuration, some options cause run-time errors because the requested SSL or TLS versions are not supported by the particular installed TLS library. Be sure to test well before you deploy for unattended operation!

  'auto'

    (default, the same as TLS1.2+). Since v6.4.0, changed in v6.5.0. Require TLS. Auto-negotiate TLSv1.2 or newer, disable downgrade below. (older fetchmail versions than v6.5.0 have auto-negotiated older protocols, v6.4.x would permit TLSv1.0 by default, v6.3.x would permit SSLv3).

  '', the empty string

    Disable STARTTLS. If --ssl is given for the same server, log an error and pretend that 'auto' had been used instead.

  'SSL23'

    see 'auto'. Deprecated, recognized for backwards compatibility.

  'TLS'

    see 'auto'. For symmetry with OpenSSL client method names.

  'TLS1'

    Require TLSv1. This does not negotiate TLSv1.1 or newer, and is discouraged. Replace by TLS1+ unless the latter chokes your server.

  'TLS1+'

    Since v6.4.0. This is an auto-negotiation feature that will permit TLSv1.0 and newer.

  'TLS1.1'

    Since v6.4.0. Require TLS v1.1 exactly.

  'TLS1.1+'

    Since v6.4.0. Require TLS. Auto-negotiate TLSv1.1 or newer.

  'TLS1.2'

    Since v6.4.0. Require TLS v1.2 exactly.

  'TLS1.2+'

    Since v6.4.0. Require TLS. Auto-negotiate TLSv1.2 or newer. This is the default in fetchmail v6.5.x.

  'TLS1.3'

    Since v6.4.0. Require TLS v1.3 exactly.

  'TLS1.3+'

    Since v6.4.0. Require TLS. Auto-negotiate TLSv1.3 or newer.

  Unrecognized parameters

    are treated the same as 'auto'.

  NOTE: you should hardly ever need to use anything other than '' (to force an unencrypted connection) or 'auto' (to enforce TLS).

--sslcertck
  (Keyword: sslcertck, default enabled since v6.4.0)
  --sslcertck causes fetchmail to require that SSL/TLS be used and disconnect unless it can successfully negotiate SSL or TLS, or if it cannot successfully verify and validate the certificate and follow it to a trust anchor (or trusted root certificate). The trust anchors are given as a set of local trusted certificates (see the sslcertfile and sslcertpath options). If the server certificate cannot be obtained or is not signed by one of the trusted ones (directly or indirectly), fetchmail will disconnect, regardless of the sslfingerprint option.
--nosslcertck
  (Keyword: no sslcertck, only in v6.4.X)
  The opposite of --sslcertck, this is a discouraged option. It permits fetchmail to continue connecting even if the server certificate failed the verification checks. Should only be used together with --sslfingerprint.
--sslcertfile <file>
  (Keyword: sslcertfile, since v6.3.17)
  Sets the file fetchmail uses to look up local certificates. The default is empty. This can be given in addition to --sslcertpath below, and certificates specified in --sslcertfile will be processed before those in --sslcertpath. The option can be used in addition to --sslcertpath.

  The file is a text file. It contains the concatenation of trusted CA certificates in PEM format.

  Note that using this option will suppress loading the default SSL trusted CA certificates file unless you set the environment variable FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS to a non-empty value.

--sslcertpath <directory>
  (Keyword: sslcertpath)
  Sets the directory fetchmail uses to look up local certificates. The default is your OpenSSL default directory. The directory must be hashed the way OpenSSL expects it - every time you add or modify a certificate in the directory, you need to use the c_rehash tool (which comes with OpenSSL in the tools/ sub-directory). Also, after OpenSSL upgrades, you may need to run c_rehash.

  This can be given in addition to --sslcertfile above, which see for precedence rules.

  Note that using this option will suppress adding the default SSL trusted CA certificates directory unless you set the environment variable FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS to a non-empty value.

--sslcommonname <common name>
  (Keyword: sslcommonname; since v6.3.9)
  Use of this option is discouraged. Before using it, contact the administrator of your upstream server and ask for a proper SSL certificate to be used. If that cannot be attained, this option can be used to specify the name (CommonName) that fetchmail expects on the server certificate. A correctly configured server will have this set to the host name by which it is reached, and by default fetchmail will expect as much. Use this option when the CommonName is set to some other value, to avoid the "Server CommonName mismatch" warning, and only if the upstream server's operator cannot be made to use proper certificates.
--sslfingerprint [{<algo>}]<fingerprint>
  (Keyword: sslfingerprint)
  Specify the fingerprint of the server key in hexadecimal notation with colons separating groups of two digits. This is the format that fetchmail uses to report the fingerprint when an SSL connection is established. When this is specified, fetchmail will compare the server key fingerprint with the given one, and the connection will fail if they do not match, regardless of the sslcertck setting. The connection will also fail if fetchmail cannot obtain an SSL certificate from the server. This can be used to prevent man-in-the-middle attacks, but the finger print from the server must be obtained or verified over a secure channel, and certainly not over the same Internet connection that fetchmail would use.

  The fingerprint can be prefixed with an EVP_MD digest algorithm name in curly braces, for instance, {MD5}00:01:...:0F. All digest algorithms that your SSL provider library supports can be used. Choose a sensible one, for instance, SHA256. If the {algo} prefix is omitted, MD5 is used for compatibility with fetchmail 6.4 and older.

  Using this option will prevent printing certificate verification errors as long as --nosslcertck is in effect.

  If you just want the --verbose log output to switch logging to a different hash, without pinning the server's certificate hash, you can use --sslfingerprint '{algo}*', f.i., --sslfingerprint '{SHA256}*'

  To obtain the fingerprint of a certificate stored in the file cert.pem, try:

    openssl x509 -in cert.pem -noout -sha256 -fingerprint

For details, see x509(1ssl).

### Delivery Control Options

-S <hosts> | --smtphost <hosts>
  (Keyword: smtp[host])
  (since v6.6.0, fetchmail supports TLS and STARTTLS for SMTP hosts)
  (since v6.5.6, fetchmail knows how to generate RFC-5321 IP address literals from a bare numeric-address IPv4 or IPv6 string)
  Specify a hunt list of hosts to forward mail to (one or more host names, comma-separated). Hosts are tried in list order; the first one that is up becomes the forwarding target for the current run. If this option is not specified, 'localhost' is used as the default. Each host name may have a port number following the host name. The port number is separated from the host name by a slash; the default port is "smtp". If you specify an absolute path name (beginning with a /), it will be interpreted as the name of a UNIX socket accepting LMTP connections (such as is supported by the Cyrus IMAP daemon).
  Example:

    --smtphost server1,server2/2525,server3,/var/imap/socket/lmtp

This option can be used with ODMR, and will make fetchmail a relay between the ODMR server and SMTP or LMTP receiver.

> Each host name for SMTP servers supports up to four options separated with a slash (/):

> /25 or /587 or /smtp or /465 or /smtps

>   25 or any other number between 1 and 65535 designates the port number to connect to; smtp or any other service name that the system can resolve (simple setups may use /etc/services); if not given, fetchmail will use default port numbers as described below.

> One of

> > `/notls`

> >   disables opportunistic STARTTLS even if offered by the server. This is implied if the hostname is localhost exactly.

> > `/starttls`

> >   requires the server to offer STARTTLS in the Extended Hello (EHLO) and requires that the server certificate validates as if --sslcertck had been set. The default port will be 25.

> > `/tls`

> >   negotiates TLS wrapping before exchanging the greeting and requires that the server certificate validates as if --sslcertck had been set. The default port will be 465.

> None of /notls, /tls, /starttls:

>   opportunistic TLS (except for localhost, see above). Will try to negotiate STARTTLS if offered by the server, but will not insist on certificate validation, as if by --nosslcertck.

> `/tlsproto=PROTO`

>   behaves as though --sslproto PROTO had been given, which see. Ignored if /notls is active.

> `/servername=NAME`

>   switches the expected X.509 certificate name to NAME and will pass it through Server Name Indication (SNI) if the SMTP service multiplexes by server name. Ignored if /notls is active.

> NOTE 1: any text not recognized explicitly will be considered a service name; syntax errors such as mistyped options can show up as confusing getaddrinfo() errors to resolve a service, for instance, as 'Servname not supported for ai_socktype'.

> NOTE 2: when contradictory options are given, the last one given prevails

> Example:

    --smtphost dnsname.example.org/25/starttls/tlsproto=tls1.3/servername=commonname.example.com

would resolve dnsname.example.org, connect to it on port 25, try to issue an STARTTLS command and upgrade to TLS v1.3 and expect that the server's X.509 certificate matches the name commonname.example.com.

> WARNING for versions 6.5.5 and before: if you use address numeric IP addresses here, be sure to use --smtpaddress or --smtpname (either of which see) with a valid SMTP address literal!

--esmtpname <authid>

  (since v6.5.7; Keyword: esmtpname, since v5.9.9) Sets the authorization ID for SMTP AUTH to be used for logging into the SMTP server. Defaults to fetchmail's notion of the running user, taken from the first defined environment variable FETCHMAILUSER, LOGNAME, USER. (not currently listed in --help output)

  NOTE: This is per "poll" and will be the same for all servers listed in your smtphost list!

  NOTE: fetchmail does not currently enforce that the connection goes via loopback interface or TLS secured encrypted layer - be sure to enforce TLS or STARTTLS on the SMTP server if it's not your localhost.

--esmtppassword <secret>

  (since v6.5.7; Keyword: esmtppassword, since v5.9.9) Sets the secret/password for SMTP AUTH to be used for logging into the SMTP server. (not currently listed in --help output)

  NOTE 1: instead of in fetchmail's rcfile, you can put the password into the

which see.

> NOTE 2: This is per "poll" and will be the same for all servers listed in your smtphost list! The password will be taken for the first smtphost, or it's /servername= option in the list that does have a .netrc entry.

> NOTE 3: fetchmail does not currently enforce that the connection goes via loopback interface or TLS secured encrypted layer - be sure to enforce TLS or STARTTLS on the SMTP server if it's not your localhost.

--fetchdomains <hosts>
  (Keyword: fetchdomains)
  In ETRN or ODMR mode, this option specifies the list of domains the server should ship mail for once the connection is turned around. The default is the FQDN of the machine running fetchmail.
-D <domain> | --smtpaddress <domain>
  (Keyword: smtpaddress)
  Specify the domain to be appended to addresses in RCPT TO lines shipped to SMTP. When this is not specified, the name of the SMTP server (as specified by --smtphost) is used for SMTP/LMTP and 'localhost' is used for UNIX socket/BSMTP.

  NOTE: if you intend to use numeric addresses with fetchmail 6.5.5 or older, or so-called address literals per the SMTP standard, write them in proper SMTP syntax, for instance --smtpaddress "[192.0.2.6]" or --smtpaddress "[IPv6:2001:DB8::6]".

--smtpname <user@domain>
  (Keyword: smtpname)
  Specify the user and domain to be put in RCPT TO lines shipped to SMTP. The default user is the current local user. Please also see the NOTE about --smtpaddress and address literals above.
-Z <nnn> | --antispam <nnn[, nnn]...>
  (Keyword: antispam)
  Specifies the list of numeric SMTP errors that are to be interpreted as a spam-block response from the listener. A value of -1 disables this option. For the command-line option, the list values should be comma-separated. Note that the antispam values only apply to "MAIL FROM" responses in the SMTP/LMTP dialogue, but several MTAs (Postfix in its default configuration, qmail) defer the anti-spam response code until after the RCPT TO. --antispam does not work in these circumstances. Also see --softbounce (default) and its inverse.
-m <command> | --mda <command>
  (Keyword: mda)
  This option lets fetchmail use a Message or Local Delivery Agent (MDA or LDA) directly, rather than forward via SMTP or LMTP.

  To avoid losing mail, use this option only with MDAs like maildrop or MTAs like sendmail that exit with a nonzero status on disk-full and other delivery errors; the nonzero status tells fetchmail that delivery failed and prevents the message from being deleted on the server.

  If fetchmail is running as root, it sets its user id while delivering mail through an MDA as follows: First, the FETCHMAILUSER, LOGNAME, and USER environment variables are checked in this order. The value of the first variable from his list that is defined (even if it is empty!) is looked up in the system user database. If none of the variables is defined, fetchmail will use the real user id it was started with. If one of the variables was defined, but the user stated there is not found, fetchmail continues running as root, without checking remaining variables on the list. Practically, this means that if you run fetchmail as root (not recommended), it is most useful to define the FETCHMAILUSER environment variable to set the user that the MDA should run as. Some MDAs (such as maildrop) are designed to be setuid root and setuid to the recipient's user id, so you do not lose functionality this way even when running fetchmail as unprivileged user. Check the MDA's manual for details.

Some possible MDAs are "/usr/sbin/sendmail -i -f %F -- %T" (Note: some several older or vendor sendmail versions mistake -- for an address, rather than an indicator to mark the end of the option arguments), "/usr/bin/deliver" and "/usr/bin/maildrop -d %T". Local delivery addresses will be inserted into the MDA command wherever you place a %T; the mail message's From address will be inserted where you place an %F.

Do NOT enclose the %F or %T string in single quotes! For both %T and %F, fetchmail encloses the addresses in single quotes ('), after removing any single quotes they may contain, before the MDA command is passed to the shell.

Do NOT use an MDA invocation that dispatches on the contents of To/Cc/Bcc, like "sendmail -i -t" or "qmail-inject", it will create mail loops and bring the just wrath of many postmasters down upon your head. This is one of the most frequent configuration errors!

Also, do not try to combine multidrop mode with an MDA such as maildrop that can only accept one address, unless your upstream stores one copy of the message per recipient and transports the envelope recipient in a header; you will lose mail.

The well-known procmail(1) package is very hard to configure properly, it has a very nasty "fall through to the next rule" behavior on delivery errors (even temporary ones, such as out of disk space if another user's mail daemon copies the mailbox around to purge old messages), so your mail will end up in the wrong mailbox sooner or later. The proper procmail configuration is outside the scope of this document. Using maildrop(1) is usually much easier, and many users find the filter syntax used by maildrop easier to understand.

Finally, we strongly advise that you do not use qmail-inject. The command line interface is non-standard without providing benefits for typical use, and fetchmail makes no attempts to accommodate qmail-inject's deviations from the standard. Some of qmail-inject's command-line and environment options are actually dangerous and can cause broken threads, non-detected duplicate messages and forwarding loops.

--lmtp
  (Keyword: lmtp)
  Cause delivery via LMTP (Local Mail Transfer Protocol). A service host and port must be explicitly specified on each host in the smtphost hunt list (see above) if this option is selected; the default port 25 will (in accordance with RFC 2033) not be accepted.
--bsmtp <filename>
  (Keyword: bsmtp)
  Append fetched mail to a BSMTP file. This simply contains the SMTP commands that would normally be generated by fetchmail when passing mail to an SMTP listener daemon.

An argument of '-' causes the SMTP batch to be written to standard output, which is of limited use: this only makes sense for debugging, because fetchmail's regular output is interspersed on the same channel, so this is not suitable for mail delivery. This special mode may be removed in a later release.

Note that fetchmail's reconstruction of MAIL FROM and RCPT TO lines is not guaranteed correct; the caveats discussed under THE USE AND ABUSE OF MULTIDROP MAILBOXES below apply. This mode has precedence before --mda and SMTP/LMTP.

--bad-header {reject|accept}
  (Keyword: bad-header; since v6.3.15)
  Specify how fetchmail is supposed to treat messages with bad headers, i.e., headers with bad syntax. Traditionally, fetchmail has rejected such messages, but some distributors modified fetchmail to accept them. You can now configure fetchmail's behaviour per server.

### Resource Limit Control Options

-l <maxbytes> | --limit <maxbytes>
  (Keyword: limit)
  Takes a maximum octet size argument, where 0 is the default and also the special value designating "no limit". If nonzero, messages larger than this size will not be fetched and will be left on the server (in foreground sessions, the progress messages will note that they are "oversized"). If the fetch protocol permits (in particular, under IMAP or POP3 without the fetchall option) the message will not be marked seen.

An explicit --limit of 0 overrides any limits set in your run control file. This option is intended for those needing to strictly control fetch time due to expensive and variable phone rates.

Combined with --limitflush, it can be used to delete oversized messages waiting on a server. In daemon mode, oversize notifications are mailed to the calling user (see the --warnings option). This option does not work with ETRN or ODMR.

-w <interval> | --warnings <interval>
  (Keyword: warnings)
  Takes an interval in seconds. When you call fetchmail with a 'limit' option in daemon mode, this controls the interval at which warnings about oversized messages are mailed to the calling user (or the user specified by the 'postmaster' option). One such notification is always mailed at the end of the first poll that the oversized message is detected. Thereafter, re-notification is suppressed until after the warning interval elapses (it will take place at the end of the first following poll).
-b <count> | --batchlimit <count>
  (Keyword: batchlimit)
  Specify the maximum number of messages that will be shipped to an SMTP listener before the connection is deliberately torn down and rebuilt (defaults to 0, meaning no limit). An explicit --batchlimit of 0 overrides any limits set in your run control file. While sendmail(8) normally initiates delivery of a message immediately after receiving the message terminator, some SMTP listeners are not so prompt. MTAs like smail(8) may wait till the delivery socket is shut down to deliver. This may produce annoying delays when fetchmail is processing very large batches. Setting the batch limit to some nonzero size will prevent these delays. This option does not work with ETRN or ODMR.
-B <number> | --fetchlimit <number>
  (Keyword: fetchlimit)
  Limit the number of messages accepted from a given server in a single poll. By default there is no limit. An explicit --fetchlimit of 0 overrides any limits set in your run control file. This option does not work with ETRN or ODMR.
--fetchsizelimit <number>
  (Keyword: fetchsizelimit)
  Limit the number of sizes of messages accepted from a given server in a single transaction. This option is useful in reducing the delay in downloading the first mail when there are too many mails in the mailbox. By default, the limit is 100. If set to 0, sizes of all messages are downloaded at the start. This option does not work with ETRN or ODMR. For POP3, the only valid non-zero value is 1.
--fastuidl <number>
  (Keyword: fastuidl)
  Do a binary instead of linear search for the first unseen UID. Binary search avoids downloading the UIDs of all mails. This saves time (especially in daemon mode) where downloading the same set of UIDs in each poll is a waste of bandwidth. The number 'n' indicates how rarely a linear search should be done. In daemon mode, linear search is used once followed by binary searches in 'n-1' polls if 'n' is greater than 1; binary search is always used if 'n' is 1; linear search is always used if 'n' is 0. In non-daemon mode, binary search is used if 'n' is 1; otherwise linear search is used. The default value of 'n' is 4. This option works with POP3 only.
-e <count> | --expunge <count>
  (Keyword: expunge)
  Arrange for deletions to be made final after a given number of messages. Under POP2 or POP3, fetchmail cannot make deletions final without sending QUIT and ending the session -- with this option on, fetchmail will break a long mail retrieval session into multiple sub-sessions, sending QUIT after each sub-session. This is a good defense against line drops on POP3 servers. Under IMAP, fetchmail normally issues an EXPUNGE command after each deletion in order to force the deletion to be done immediately. This is safest when your connection to the server is flaky and expensive, as it avoids re-sending duplicate mail after a line hit. However, on large mailboxes the overhead of re-indexing after every message can slam the server pretty hard, so if your connection is reliable it is good to do expunges less frequently. Also note that some servers enforce a delay of a few seconds after each quit, so fetchmail may not be able to get back in immediately after an expunge -- you may see "lock busy" errors if this happens. If you specify this option to an integer N, it tells fetchmail to only issue expunges on every Nth delete. An argument of zero suppresses expunges entirely (so no expunges at all will be done until the end of run). This option does not work with ETRN or ODMR.

### Authentication Options

-u <name> | --user <name> | --username <name>
  (Keyword: user[name])
  Specifies the user identification to be used when logging in to the mail server. The appropriate user identification is both server and user-dependent. The default is your login name on the client machine that is running fetchmail. See USER AUTHENTICATION below for a complete description.
-I <specification> | --interface <specification>
  (Keyword: interface)
  Require that a specific interface device be up and have a specific local or remote IPv4 (IPv6 is not supported by this option yet) address (or range) before polling. Frequently fetchmail is used over a transient point-to-point TCP/IP link established directly to a mail server via SLIP or PPP. That is a relatively secure channel. But when other TCP/IP routes to the mail server exist (e.g., when the link is connected to an alternate ISP), your username and password may be vulnerable to snooping (especially when daemon mode automatically polls for mail, shipping a clear password over the net at predictable intervals). The --interface option may be used to prevent this. When the specified link is not up or is not connected to a matching IP address, polling will be skipped. The format is:

    interface/iii.iii.iii.iii[/mmm.mmm.mmm.mmm]

The field before the first slash is the interface name (i.e., sl0, ppp0 etc.). The field before the second slash is the acceptable IP address. The field after the second slash is a mask which specifies a range of IP addresses to accept. If no mask is present 255.255.255.255 is assumed (i.e., an exact match). This option is currently only supported under Linux and FreeBSD. Please see the monitor section for below for FreeBSD specific information.

Note that this option may be removed from a future fetchmail version.

-M <interface> | --monitor <interface>
  (Keyword: monitor)
  Daemon mode can cause transient links which are automatically taken down after a period of inactivity (e.g., PPP links) to remain up indefinitely. This option identifies a system TCP/IP interface to be monitored for activity. After each poll interval, if the link is up but no other activity has occurred on the link, then the poll will be skipped. However, when fetchmail is woken up by a signal, the monitor check is skipped and the poll goes through unconditionally. This option is currently only supported under Linux and FreeBSD. For the monitor and interface options to work for non root users under FreeBSD, the fetchmail binary must be installed setgid kmem. This would be a security hole, but fetchmail runs with the effective GID set to that of the kmem group only when interface data is being collected.

Note that this option may be removed from a future fetchmail version.

--auth <type>
  (Keyword: auth[enticate])
  This option permits you to specify an authentication type (see USER AUTHENTICATION below for details). The possible values are any, password, kerberos_v5, kerberos (or, for excruciating exactness, kerberos_v4), gssapi, cram-md5, otp, ntlm, msn (only for POP3), external (only IMAP) and implicit (ssh is understood as alias for implicit). When any (the default) is specified, fetchmail tries first methods that do not require a password (EXTERNAL, GSSAPI, KERBEROS IV, KERBEROS 5); then it looks for methods that mask your password (CRAM-MD5, NTLM, X-OTP - note that MSN is only supported for POP3, but not auto-probed); and only if the server does not support any of those will it ship your password unencrypted. Other values may be used to force various authentication methods: implicit suppresses authentication and is thus useful for IMAP PREAUTH (if you are using a secure --plugin, for instance, a properly configured ssh, you may also need to set --sslproto '' or, in the rcfile, sslproto '', in order to avoid fetchmail negotiating STARTTLS over SSH). external suppresses authentication and is thus useful for IMAP EXTERNAL. Any value other than password, cram-md5, ntlm, msn or otp suppresses fetchmail's normal inquiry for a password. Specify implicit when you are using an end-to-end secure connection such as an ssh tunnel (in this case you may also want to specify --sslproto '', which see); specify external when you use TLS with client authentication and specify gssapi or kerberos_v4 if you are using a protocol variant that employs GSSAPI or K4. Choosing KPOP protocol automatically selects Kerberos authentication. This option does not work with ETRN. GSSAPI service names are in line with RFC-2743 and IANA registrations, see Generic Security Service Application Program Interface (GSSAPI)/Kerberos/SimpleAuthentication and Security Layer (SASL) Service Names.

### Miscellaneous Options

-f <pathname> | --fetchmailrc <pathname>

  Specify a non-default name for the ~/.fetchmailrc run control file. The pathname argument must be either "-" (a single dash, meaning to read the configuration from standard input) or a filename. Unless the --version option is also on, a named file argument must have permissions no more open than 0700 (u=rwx,g=,o=) or else be /dev/null.

-i <pathname> | --idfile <pathname>
  (Keyword: idfile)
  Specify an alternate name for the .fetchids file used to save message UIDs. NOTE: since fetchmail 6.3.0, write access to the directory containing the idfile is required, as fetchmail writes a temporary file and renames it into the place of the real idfile only if the temporary file has been written successfully. This avoids the truncation of idfiles when running out of disk space.
--pidfile <pathname>
  (Keyword: pidfile; since fetchmail v6.3.4)
  Override the default location of the PID file that is used as a lock file. Default: see "ENVIRONMENT" below. Note that many places in the code and documentation, the term "lock file" is used. This file contains the process ID of the running fetchmail on the first line and potentially the daemon interval on a second line.
-n | --norewrite
  (Keyword: no rewrite)
  Normally, fetchmail edits RFC-822 address headers (To, From, Cc, Bcc, and Reply-To) in fetched mail so that any mail IDs local to the server are expanded to full addresses (@ and the mail server host name are appended). This enables replies on the client to get addressed correctly (otherwise your mailer might think they should be addressed to local users on the client machine!). This option disables the rewrite. (This option is provided to pacify people who are paranoid about having an MTA edit mail headers and want to know they can prevent it, but it is generally not a good idea to actually turn off rewrite.) When using ETRN or ODMR, the rewrite option is ineffective.
-E <line> | --envelope <line>
  (Keyword: envelope; Multidrop only)
  In the configuration file, an enhanced syntax is used:
  envelope [<count>] <line>

This option changes the header fetchmail assumes will carry a copy of the mail's envelope address. Normally this is 'X-Envelope-To'. Other typically found headers to carry envelope information are 'X-Original-To' and 'Delivered-To'. Now, since these headers are not standardized, practice varies. See the discussion of multidrop address handling below. As a special case, 'envelope "Received"' enables parsing of sendmail-style Received lines. This is the default, but discouraged because it is not fully reliable.

Note that fetchmail expects the Received-line to be in a specific format: It must contain "by host for address", where host must match one of the mail server names that fetchmail recognizes for the account in question.

The optional count argument (only available in the configuration file) determines how many header lines of this kind are skipped. A count of 1 means: skip the first, take the second. A count of 2 means: skip the first and second, take the third, and so on.

-Q <prefix> | --qvirtual <prefix>
  (Keyword: qvirtual; Multidrop only)
  The string prefix assigned to this option will be removed from the user name found in the header specified with the envelope option (before doing multidrop name mapping or localdomain checking, if either is applicable). This option is useful if you are using fetchmail to collect the mail for an entire domain and your ISP (or your mail redirection provider) is using qmail. One of the basic features of qmail is the Delivered-To: message header. Whenever qmail delivers a message to a local mailbox it puts the username and host name of the envelope recipient on this line. The major reason for this is to prevent mail loops. To set up qmail to batch mail for a disconnected site the ISP-mailhost will have normally put that site in its 'Virtualhosts' control file so it will add a prefix to all mail addresses for this site. This results in mail sent to 'username@userhost.userdom.dom.com' having a Delivered-To: line of the form:

  Delivered-To: mbox-userstr-username@userhost.example.com

  The ISP can make the 'mbox-userstr-' prefix anything they choose but a string matching the user host name is likely. By using the option 'envelope Delivered-To:' you can make fetchmail reliably identify the original envelope recipient, but you have to strip the 'mbox-userstr-' prefix to deliver to the correct user. This is what this option is for.

--configdump

  Parse the ~/.fetchmailrc file, interpret any command-line options specified, and dump a configuration report to standard output. The configuration report is a data structure assignment in the language Python. This option is meant to be used with an interactive ~/.fetchmailrc editor like fetchmailconf, written in Python.

-y | --yydebug

  Enables parser debugging, this option is meant to be used by developers only.

### Removed Options

-T | --netsec

  Removed before version 6.3.0, the required underlying inet6_apps library had been discontinued and is no longer available.

## USER AUTHENTICATION AND ENCRYPTION

All modes except ETRN require authentication of the client to the server. Normal user authentication in fetchmail is very much like the authentication mechanism of ftp(1). The correct user-id and password depend upon the underlying security system at the mail server.

If the mail server is a Unix machine on which you have an ordinary user account, your regular login name and password are used with fetchmail. If you use the same login name on both the server and the client machines, you needn't worry about specifying a user-id with the -u option -- the default behavior is to use your login name on the client machine as the user-id on the server machine. If you use a different login name on the server machine, specify that login name with the -u option. E.g., if your login name is 'jsmith' on a machine named 'mailgrunt', you would start fetchmail as follows:

> fetchmail -u jsmith mailgrunt

The default behavior of fetchmail is to prompt you for your mail server password before the connection is established. This is the safest way to use fetchmail and ensures that your password will not be compromised. You may also specify your password in your ~/.fetchmailrc file. This is convenient when using fetchmail in daemon mode or with scripts.

### Using netrc files

If you do not specify a password, and fetchmail cannot extract one from your ~/.fetchmailrc file, it will look for a ~/.netrc file in your home directory before requesting one interactively; if an entry matching the mail server is found in that file, the password will be used. Fetchmail first looks for a match on poll name; if it finds none, it checks for a match on via name. To show a practical example, a .netrc might look like this:

    machine hermes.example.org
    login joe
    password topsecret

You can repeat this block with different user information if you need to provide more than one password.

This feature may allow you to avoid duplicating password information in more than one file.

The netrc file contains login information originally set for ftp(1) but fetchmail understands typical constructs of this file to use it for passwords. The syntax consists of tokens (usually in pairs with strings). Strings can be quoted with single or double quotes, as in "quoted string", to allow enclosing blanks, and a backslash (\) within a quoted string will escape the following character, so that a password can contain quote marks themselves. Tokens are separated by spaces, tabs or newline characters.

These tokens are understood:

machine name

  Identify a remote computer name for which the following tokens apply. It needs to match either fetchmail's poll or via name.

login name

  Defines the user name that fetchmail would match when looking for entries. Fetchmail ignores zero-length names or entries without login.

password string

  Defines the password that fetchmail will use when machine and login match the poll/via name and the username.

default

  This is like machine, but would match any name. Fetchmail ignores it. After this, no more machine sections are permitted.

account string

  Fetchmail ignores this token/string pair.

macdef macro_name

  Fetchmail ignores this macro definition, meaning this, the remainder of the lines, and all following lines until a blank line is found (i. e., two consecutive new-line characters). Then .netrc parsing resumes.

On mail servers that do not provide ordinary user accounts, your user-id and password are usually assigned by the server administrator when you apply for a mailbox on the server. Contact your server administrator if you do not know the correct user-id and password for your mailbox account.

### Secure Socket Layers (SSL) and Transport Layer Security (TLS)

All retrieval protocols can use SSL or TLS wrapping for the transport. Additionally, POP3 and IMAP retrieval can also negotiate SSL/TLS by means of STARTTLS (or STLS).

You can access TLS-encrypted services by specifying the options starting with --ssl, such as --ssl, --sslproto, --nosslcertck, and others. You can also do this using the corresponding user options in the .fetchmailrc file. Some services, such as POP3 and IMAP, have different well known ports defined for the SSL encrypted services. The encrypted ports will be selected automatically when SSL is enabled and no explicit port is specified. Also, the --sslcertck command line or sslcertck run control file option should be used at least in documentation to force strict certificate checking with older fetchmail versions - see below.

If TLS or SSL is not configured, fetchmail will usually still try to use STARTTLS. In practice, TLS or SSL it still mandatory because --sslcertck is a default setting and implicitly requires STARTTLS.

STARTTLS can be enforced by using --sslproto auto and defeated by using --sslproto ''. STARTTLS connections use the same port as the unencrypted version of the protocol and negotiate TLS via special command. The --sslcertck command line or sslcertck run control file option should be used to force strict certificate checking - see below.

--sslcertck is recommended: When connecting to an SSL or TLS encrypted server, the server presents a certificate to the client for validation. The certificate is checked to verify that the common name in the certificate matches the name of the server being contacted and that the effective and expiration dates in the certificate indicate that it is currently valid. If any of these checks fail, a warning message is printed, but the connection continues. The server certificate does not need to be signed by any specific Certifying Authority and may be a "self-signed" certificate. If the --sslcertck command line option or sslcertck run control file option is used, fetchmail will instead abort if any of these checks fail, because it must assume that there is a man-in-the-middle attack in this scenario, hence fetchmail must not expose clear-text passwords. Use of the sslcertck or --sslcertck option is therefore advised; it has become the default in fetchmail 6.4.0.

Some SSL encrypted servers may request a client side certificate. A client side public SSL certificate and private SSL key may be specified. If requested by the server, the client certificate is sent to the server for validation. Some servers may require a valid client certificate and may refuse connections if a certificate is not provided or if the certificate is not valid. Some servers may require client side certificates be signed by a recognized Certifying Authority. The format for the key files and the certificate files is that required by the underlying SSL libraries (OpenSSL in the general case).

A word of care about the use of SSL: While above mentioned setup with self-signed server certificates retrieved over the wires can protect you from a passive eavesdropper, it does not help against an active attacker. It is clearly an improvement over sending the passwords in clear, but you should be aware that a man-in-the-middle attack is trivially possible (in particular with tools such as dsniff). Use of strict certificate checking with a certification authority recognized by server and client, or perhaps of an SSH tunnel (see below for some examples) is preferable if you care seriously about the security of your mailbox and passwords.

## POP3 VARIANTS

Early versions of POP3 (RFC1081, RFC1225) supported a crude form of independent authentication using the .rhosts file on the mail server side. Under this RPOP variant, a fixed per-user ID equivalent to a password was sent in clear over a link to a reserved port, with the command RPOP rather than PASS to alert the server that it should do special checking. RPOP is supported by fetchmail (you can specify 'protocol RPOP' to have the program send 'RPOP' rather than 'PASS') but its use is strongly discouraged, and support will be removed from a future fetchmail version. This facility was vulnerable to spoofing and was withdrawn in RFC1460.

RFC1460 introduced APOP authentication. In this variant of POP3, you register an APOP password on your server host (on some servers, the program to do this is called popauth(8)). You put the same password in your ~/.fetchmailrc file. Each time fetchmail logs in, it sends an MD5 hash of your password and the server greeting time to the server, which can verify it by checking its authorization database.

Note that APOP is no longer considered resistant against man-in-the-middle attacks.

### RETR or TOP

fetchmail makes some efforts to make the server believe messages had not been retrieved, by using the TOP command with a large number of lines when possible. TOP is a command that retrieves the full header and a fetchmail-specified amount of body lines. It is optional and therefore not implemented by all servers, and some are known to implement it improperly. On many servers however, the RETR command which retrieves the full message with header and body, sets the "seen" flag (for instance, in a web interface), whereas the TOP command does not do that.

fetchmail will always use the RETR command if "fetchall" is set. fetchmail will also use the RETR command if "keep" is set and "uidl" is unset. Finally, fetchmail will use the RETR command on Maillennium POP3/PROXY servers (used by Comcast) to avoid a deliberate TOP misinterpretation in this server that causes message corruption.

In all other cases, fetchmail will use the TOP command. This implies that in "keep" setups, "uidl" must be set if "TOP" is desired.

Note that this description is true for the current version of fetchmail, but the behavior may change in future versions. In particular, fetchmail may prefer the RETR command because the TOP command causes much grief on some servers and is only optional.

## ALTERNATE AUTHENTICATION FORMS/METHODS

If your fetchmail was built with Kerberos support and you specify Kerberos authentication (either with --auth or the .fetchmailrc option authenticate kerberos_v4) it will try to get a Kerberos ticket from the mail server at the start of each query. Note: if either the pollname or via name is 'hesiod', fetchmail will try to use Hesiod to look up the mail server.

If you use POP3 or IMAP with GSSAPI authentication, fetchmail will expect the server to have RFC1731- or RFC1734-conforming GSSAPI capability, and will use it. Currently this has only been tested over Kerberos 5, so you are expected to already have a ticket-granting ticket. You may pass a username different from your principal name using the standard --user command or by the .fetchmailrc option user.

If your IMAP daemon returns the PREAUTH response in its greeting line, fetchmail will notice this and skip the normal authentication step. This can be useful, e.g., if you start imapd explicitly using ssh. In this case you can declare the authentication value 'implicit' on that site entry to stop .fetchmail from asking you for a password when it starts up.

If you use client authentication with TLS1 and your IMAP daemon returns the AUTH=EXTERNAL response, fetchmail will notice this and will use the authentication shortcut and will not send the passphrase. In this case you can declare the authentication value 'external' on that site to stop fetchmail from asking you for a password when it starts up.

If you are using POP3, and the server issues a one-time-password challenge conforming to RFC1938, fetchmail will use your password as a pass phrase to generate the required response. This avoids sending secrets over the net unencrypted.

Compuserve's RPA authentication is supported. If you compile in the support, fetchmail will try to perform an RPA pass-phrase authentication instead of sending over the password unencrypted if it detects "@compuserve.com" in the host name.

If you are using IMAP, Microsoft's NTLM authentication (used by Microsoft Exchange) is supported. If you compile in the support, fetchmail will try to perform an NTLM authentication (instead of sending over the password unencrypted) whenever the server returns AUTH=NTLM in its capability response. Specify a user option value that looks like 'user@domain': the part to the left of the @ will be passed as the username and the part to the right as the NTLM domain.

### ESMTP AUTH

fetchmail also supports authentication to the ESMTP server on the client side according to RFC 4952. Supported authentication mechanisms are CRAM-MD5, PLAIN and in fetchmail 6.5.X the obsolete LOGIN. You can specify a name/password pair to be used with the keywords 'esmtpname' and 'esmtppassword'; the former defaults to the username of the calling user.

## DAEMON MODE

### Introducing the daemon mode

In daemon mode, fetchmail puts itself into the background and runs forever, querying each specified host and then sleeping for a given polling interval.

### Starting the daemon mode

There are several ways to make fetchmail work in daemon mode. On the command line, --daemon <interval> or -d <interval> option runs fetchmail in daemon mode. You must specify a numeric argument which is a polling interval (time to wait after completing a whole poll cycle with the last server and before starting the next poll cycle with the first server) in seconds.

Example: simply invoking

> fetchmail -d 900

will, therefore, poll all the hosts described in your ~/.fetchmailrc file (except those explicitly excluded with the 'skip' verb) a bit less often than once every 15 minutes (exactly: 15 minutes + time that the poll takes).

It is also possible to set a polling interval in your ~/.fetchmailrc file by saying 'set daemon <interval>', where <interval> is an integer number of seconds. If you do this, fetchmail will always start in daemon mode unless you override it with the command-line option --daemon 0 or -d0.

Only one daemon process is permitted per user; in daemon mode, fetchmail sets up a per-user lock file to guarantee this. (You can however cheat and set the FETCHMAILHOME environment variable to overcome this setting, but in that case, it is your responsibility to make sure you are not polling the same server with two processes at the same time.)

### Awakening the background daemon

Normally, calling fetchmail with a daemon in the background sends a wake-up signal to the daemon and quits without output. The background daemon then starts its next poll cycle immediately. The wake-up signal, SIGUSR1, can also be sent manually. The wake-up action also clears any 'wedged' flags indicating that connections have wedged due to failed authentication or multiple timeouts.

### Terminating the background daemon

The option -q or --quit will kill a running daemon process instead of waking it up (if there is no such process, fetchmail will notify you). If the --quit option appears last on the command line, fetchmail will kill the running daemon process and then quit. Otherwise, fetchmail will first kill a running daemon process and then continue running with the other options.

### Useful options for daemon mode

The -L <filename> or --logfile <filename> option (keyword: set logfile) is only effective when fetchmail is detached and in daemon mode. Note that the logfile must exist before fetchmail is run, you can use the touch(1) command with the filename as its sole argument to create it.
This option allows you to redirect status messages into a specified logfile (follow the option with the logfile name). The logfile is opened for append, so previous messages are not deleted. This is primarily useful for debugging configurations. Note that fetchmail does not detect if the logfile is rotated, the logfile is only opened once when fetchmail starts. You need to restart fetchmail after rotating the logfile and before compressing it (if applicable).
Since v6.5.0, the log file is prefixed with time stamps, in local time and in the format "Jun 20 23:45:01 fetchmail: ". It will be localized through the environment variables LC_TIME (or LC_ALL) and TZ.

The --syslog option (keyword: set syslog) allows you to redirect status and error messages emitted to the syslog(3) system daemon if available. Messages are logged with an id of fetchmail, the facility LOG_MAIL, and priorities LOG_ERR, LOG_ALERT or LOG_INFO. This option is intended for logging status and error messages which indicate the status of the daemon and the results while fetching mail from the server(s). Error messages for command line options and parsing the .fetchmailrc file are still written to stderr, or to the specified log file. The --nosyslog option turns off use of syslog(3), assuming it is turned on in the ~/.fetchmailrc file. This option is overridden, in certain situations, by --logfile (which see).

The -N or --nodetach option suppresses backgrounding and detachment of the daemon process from its control terminal. This is useful for debugging or when fetchmail runs as the child of a supervisor process such as init(8) or Gerrit Pape's runit(8). Note that this also causes the logfile option to be ignored.

Note that while running in daemon mode polling a POP2 or IMAP2bis server, transient errors (such as DNS failures or sendmail delivery refusals) may force the fetchall option on for the duration of the next polling cycle. This is a robustness feature. It means that if a message is fetched (and thus marked seen by the mail server) but not delivered locally due to some transient error, it will be re-fetched during the next poll cycle. (The IMAP logic does not delete messages until they are delivered, so this problem does not arise.)

If you touch or change the ~/.fetchmailrc file while fetchmail is running in daemon mode, this will be detected at the beginning of the next poll cycle. When a changed ~/.fetchmailrc is detected, fetchmail rereads it and restarts from scratch (using exec(2); no state information is retained in the new instance). Note that if fetchmail needs to query for passwords, of that if you break the ~/.fetchmailrc file's syntax, the new instance will softly and silently vanish away on startup.

## ADMINISTRATIVE OPTIONS

The --postmaster <name> option (keyword: set postmaster) specifies the last-resort username to which multidrop mail is to be forwarded if no matching local recipient can be found. It is also used as destination of undeliverable mail if the 'bouncemail' global option is off and additionally for spam-blocked mail if the 'bouncemail' global option is off and the 'spambounce' global option is on. This option defaults to the user who invoked fetchmail. If the invoking user is root, then the default of this option is the user 'postmaster'. Setting postmaster to the empty string causes such mail as described above to be discarded - this however is usually a bad idea. See also the description of the 'FETCHMAILUSER' environment variable in the ENVIRONMENT section below.

The --nobounce behaves like the "set no bouncemail" global option, which see.

The --invisible option (keyword: set invisible) tries to make fetchmail invisible. Normally, fetchmail behaves like any other MTA would -- it generates a Received header into each message describing its place in the chain of transmission, and tells the MTA it forwards to that the mail came from the machine fetchmail itself is running on. If the invisible option is on, the Received header is suppressed and fetchmail tries to spoof the MTA it forwards to into thinking it came directly from the mail server host.

The --showdots option (keyword: set showdots) forces fetchmail to show progress dots even if the output goes to a file or fetchmail is not in verbose mode. Fetchmail shows the dots by default when run in --verbose mode and output goes to console. This option is ignored in --silent mode.

By specifying the --tracepolls option, you can ask fetchmail to add information to the Received header on the form "polling {label} account {user}", where {label} is the account label (from the specified rcfile, normally ~/.fetchmailrc) and {user} is the username which is used to log on to the mail server. This header can be used to make filtering email where no useful header information is available and you want mail from different accounts sorted into different mailboxes (this could, for example, occur if you have an account on the same server running a mailing list, and are subscribed to the list using that account). The default is not adding any such header. In .fetchmailrc, this is called 'tracepolls'.

## RETRIEVAL FAILURE MODES

The protocols fetchmail uses to talk to mail servers are next to bulletproof. In normal operation forwarding to port 25, no message is ever deleted (or even marked for deletion) on the host until the SMTP listener on the client side has acknowledged to fetchmail that the message has been either accepted for delivery or rejected due to a spam block.

When forwarding to an MDA, however, there is more possibility of error. Some MDAs are 'safe' and reliably return a nonzero status on any delivery error, even one due to temporary resource limits. The maildrop(1) program is like this; so are most programs designed as mail transport agents, such as sendmail(1), including the sendmail wrapper of Postfix and exim(1). These programs give back a reliable positive acknowledgement and can be used with the mda option with no risk of mail loss. Unsafe MDAs, though, may return 0 even on delivery failure. If this happens, you will lose mail.

The normal mode of fetchmail is to try to download only 'new' messages, leaving untouched (and undeleted) messages you have already read directly on the server (or fetched with a previous fetchmail --keep). But you may find that messages you have already read on the server are being fetched (and deleted) even when you do not specify --all. There are several reasons this can happen.

One could be that you are using POP2. The POP2 protocol includes no representation of 'new' or 'old' state in messages, so fetchmail must treat all messages as new all the time. But POP2 is obsolete, so this is unlikely.

A potential POP3 problem might be servers that insert messages in the middle of mailboxes (some VMS implementations of mail are rumored to do this). The fetchmail code assumes that new messages are appended to the end of the mailbox; when this is not true it may treat some old messages as new and vice versa. Using UIDL whilst setting fastuidl 0 might fix this, otherwise, consider switching to IMAP.

Yet another POP3 problem is that if they cannot make temporary files in the user's home directory, some POP3 servers will hand back an undocumented response that causes fetchmail to spuriously report "No mail".

The IMAP code uses the presence or absence of the server flag \Seen to decide whether or not a message is new. This is not the right thing to do, fetchmail should check the UIDVALIDITY and use UID, but it does not do that yet. Under Unix, it counts on your IMAP server to notice the BSD-style Status flags set by mail user agents and set the \Seen flag from them when appropriate. All Unix IMAP servers we know of do this, though it is not specified by the IMAP RFCs. If you ever trip over a server that does not, the symptom will be that messages you have already read on your host will look new to the server. In this (unlikely) case, only messages you fetched with fetchmail --keep will be both undeleted and marked old.

In ETRN and ODMR modes, fetchmail does not actually retrieve messages; instead, it asks the server's SMTP listener to start a queue flush to the client via SMTP. Therefore it sends only undelivered messages.

## SPAM FILTERING

Many SMTP listeners allow administrators to set up 'spam filters' that block unsolicited email from specified domains. A MAIL FROM or DATA line that triggers this feature will elicit an SMTP response which (unfortunately) varies according to the listener.

Newer versions of sendmail return an error code of 571.

According to RFC2821, the correct thing to return in this situation is 550 "Requested action not taken: mailbox unavailable" (the draft adds "[E.g., mailbox not found, no access, or command rejected for policy reasons].").

Older versions of the exim MTA return 501 "Syntax error in parameters or arguments".

The postfix MTA runs 554 as an antispam response.

Zmailer may reject code with a 500 response (followed by an enhanced status code that contains more information).

Return codes which fetchmail treats as antispam responses and discards the message can be set with the 'antispam' option. This is one of the only three circumstance under which fetchmail ever discards mail (the others are the 552 and 553 errors described below, and the suppression of multi-dropped messages with a message-ID already seen).

If fetchmail is fetching from an IMAP server, the antispam response will be detected and the message rejected immediately after the headers have been fetched, without reading the message body. Thus, you will not pay for downloading spam message bodies.

By default, the list of antispam responses is empty.

If the spambounce global option is on, mail that is spam-blocked triggers an RFC1892/RFC1894 bounce message informing the originator that we do not accept mail from it. See also BUGS.

## SMTP/ESMTP ERROR HANDLING

Besides the spam-blocking described above, fetchmail takes special actions — that may be modified by the --softbounce option — on the following SMTP/ESMTP error response codes

452 (insufficient system storage)

  Leave the message in the server mailbox for later retrieval.

552 (message exceeds fixed maximum message size)

  Delete the message from the server. Send bounce-mail to the originator.

553 (invalid sending domain)

  Delete the message from the server. Do not even try to send bounce-mail to the originator.

Other errors greater or equal to 500 trigger bounce mail back to the originator, unless suppressed by --softbounce. See also BUGS.

## THE RUN CONTROL FILE

The preferred way to set up fetchmail is to write a .fetchmailrc file in your home directory (you may do this directly, with a text editor, or indirectly via fetchmailconf). When there is a conflict between the command-line arguments and the arguments in this file, the command-line arguments take precedence.

To protect the security of your passwords, your ~/.fetchmailrc may not normally have more than 0700 (u=rwx,g=,o=) permissions; fetchmail will complain and exit otherwise (this check is suppressed when --version is on).

You may read the .fetchmailrc file as a list of commands to be executed when fetchmail is called with no arguments.

### Run Control Syntax

Comments begin with a '#' and extend through the end of the line. Otherwise the file consists of a series of server entries or global option statements in a free-format, token-oriented syntax.

There are four kinds of tokens: grammar keywords, numbers (i.e., decimal digit sequences), unquoted strings, and quoted strings. A quoted string is bounded by double quotes and may contain whitespace (and quoted digits are treated as a string). Note that quoted strings will also contain line feed characters if they run across two or more lines, unless you use a backslash to join lines (see below). An unquoted string is any whitespace-delimited token that is neither numeric, string quoted nor contains the special characters ',', ';', ':', or '='.

Any amount of whitespace separates tokens in server entries, but is otherwise ignored. You may use backslash escape sequences (\n for LF, \t for HT, \b for BS, \r for CR, \nnn for decimal (where nnn cannot start with a 0), \0ooo for octal, and \xhh for hex) to embed non-printable characters or string delimiters in strings. In quoted strings, a backslash at the very end of a line will cause the backslash itself and the line feed (LF or NL, new line) character to be ignored, so that you can wrap long strings. Without the backslash at the line end, the line feed character would become part of the string.

Warning: while these resemble C-style escape sequences, they are not the same. fetchmail only supports these eight styles. C supports more escape sequences that consist of backslash (\) and a single character, but does not support decimal codes and does not require the leading 0 in octal notation. Example: fetchmail interprets \233 the same as \xE9 (Latin small letter e with acute), where C would interpret \233 as octal 0233 = \x9B (CSI, control sequence introducer).

Each server entry consists of one of the keywords 'poll' or 'skip', followed by a server name, followed by server options, followed by any number of user (or username) descriptions, followed by user options. Note: the most common cause of syntax errors is mixing up user and server options or putting user options before the user descriptions.

For backward compatibility, the word 'server' is a synonym for 'poll'.

You can use the noise keywords 'and', 'with', 'has', 'wants', and 'options' anywhere in an entry to make it resemble English. They are ignored, but can make entries much easier to read at a glance. The punctuation characters ':', ';' and ',' are also ignored.

### Poll versus Skip

The 'poll' verb tells fetchmail to query this host when it is run with no arguments. The 'skip' verb tells fetchmail not to poll this host unless it is explicitly named on the command line. (The 'skip' verb allows you to experiment with test entries safely, or easily disable entries for hosts that are temporarily down.)

## KEYWORD/OPTION SUMMARY

Here are the legal options. Keyword suffixes enclosed in square brackets are optional. Those corresponding to short command-line options are followed by '-' and the appropriate option letter. If option is only relevant to a single mode of operation, it is noted as 's' or 'm' for singledrop- or multidrop-mode, respectively.

Here are the legal global options:

Keyword | Opt | Mode | Function
--- | --- | --- | ---
set daemon | -d |  | Set a background poll interval in seconds.
set postmaster |  |  | Give the name of the last-resort mail recipient (default: user running fetchmail, "postmaster" if run by the root user)
set bouncemail |  |  | Direct error mail to the sender (default)
set no bouncemail |  |  | Direct error mail to the local postmaster (as per the 'postmaster' global option above).
set no spambounce |  |  | Do not bounce spam-blocked mail (default).
set spambounce |  |  | Bounce blocked spam-blocked mail (as per the 'antispam' user option) back to the destination as indicated by the 'bouncemail' global option. Warning: Do not use this to bounce spam back to the sender - most spam is sent with false sender address and thus this option hurts innocent bystanders.
set no softbounce |  |  | Delete permanently undeliverable mail. It is recommended to use this option if the configuration has been thoroughly tested.
set softbounce |  |  | Keep permanently undeliverable mail as though a temporary error had occurred (default).
set logfile | -L |  | Name of a file to append error and status messages to. Only effective in daemon mode and if fetchmail detaches. If effective, overrides set syslog.
set pidfile | -p |  | Name of the PID file.
set idfile | -i |  | Name of the file to store UID lists in.
set syslog |  |  | Do error logging through syslog(3). May be overridden by set logfile.
set no syslog |  |  | Turn off error logging through syslog(3). (default)
set properties |  |  | String value that is ignored by fetchmail (may be used by extension scripts).

Here are the legal server options:

Keyword | Opt | Mode | Function
--- | --- | --- | ---
via |  |  | Specify DNS name of mail server, overriding poll name
proto[col] | -p |  | Specify protocol (case insensitive): POP2, POP3, IMAP, APOP, KPOP
local[domains] |  | m | Specify domain(s) to be regarded as local
port |  |  | Specify TCP/IP service port (obsolete, use 'service' instead).
service | -P |  | Specify service name (a numeric value is also allowed and considered a TCP/IP port number).
auth[enticate] |  |  | Set authentication type (default 'any')
timeout | -t |  | Server inactivity timeout in seconds (default 300)
envelope | -E | m | Specify envelope-address header name
no envelope |  | m | Disable looking for envelope address
qvirtual | -Q | m | Qmail virtual domain prefix to remove from user name
aka |  | m | Specify alternate DNS names of mail server
interface | -I |  | specify IP interface(s) that must be up for server poll to take place
monitor | -M |  | Specify IP address to monitor for activity
plugin |  |  | Specify command through which to make server connections.
plugout |  |  | Specify command through which to make listener connections.
dns |  | m | Enable DNS lookup for multidrop (default)
no dns |  | m | Disable DNS lookup for multidrop
checkalias |  | m | Do comparison by IP address for multidrop
no checkalias |  | m | Do comparison by name for multidrop (default)
uidl | -U |  | Force POP3 to use client-side UIDLs (recommended)
no uidl |  |  | Turn off POP3 use of client-side UIDLs (default)
interval |  |  | Only check this site every N poll cycles; N is a numeric argument.
tracepolls |  |  | Add poll tracing information to the Received header
principal |  |  | Set Kerberos principal (only useful with IMAP and kerberos)
esmtpname |  |  | Set name for RFC2554 authentication to the ESMTP server.
esmtppassword |  |  | Set password for RFC2554 authentication to the ESMTP server.
bad-header |  |  | How to treat messages with a bad header. Can be reject (default) or accept.
idletimeout |  |  | Idle waiting timeout (in seconds), see --idle.

Here are the legal user descriptions and options:

Keyword | Opt | Mode | Function
--- | --- | --- | ---
user[name] | -u |  | This is the user description and must come first after server description and after possible server options, and before user options. It sets the remote user name if by itself or followed by 'there', or the local user name if followed by 'here'.
is |  |  | Connect local and remote user names
to |  |  | Connect local and remote user names
pass[word] |  |  | Specify remote account password
ssl |  |  | Connect to server over the specified base protocol using SSL encryption
sslcert |  |  | Specify file for client side public SSL certificate
sslcertck |  |  | Enable strict certificate checking and abort connection on failure. Default only since fetchmail v6.4.0.
no sslcertck |  |  | Disable strict certificate checking and permit connections to continue on failed verification. Discouraged. Should only be used together with sslfingerprint.
sslcertfile |  |  | Specify file with trusted CA certificates
sslcertpath |  |  | Specify c_rehash-ed directory with trusted CA certificates.
sslcommonname |  |  | specify the expected server certificate common name to match against.
sslfingerprint |  |  | Specify the expected server certificate finger print from an MD5 hash. Fetchmail will disconnect and log an error if it does not match.
sslkey |  |  | Specify file for client side private SSL key
sslproto |  |  | Force ssl protocol for connection
folder | -r |  | Specify remote folder to query
smtphost | -S |  | Specify smtp host(s) to forward to
fetchdomains |  | m | Specify domains for which mail should be fetched
smtpaddress | -D |  | Specify the domain to be put in RCPT TO lines
smtpname |  |  | Specify the user and domain to be put in RCPT TO lines
antispam | -Z |  | Specify what SMTP returns are interpreted as spam-policy blocks
mda | -m |  | Specify MDA for local delivery
bsmtp |  |  | Specify BSMTP batch file to append to
preconnect |  |  | Command to be executed before each connection
postconnect |  |  | Command to be executed after each connection
keep | -k |  | Do not delete seen messages from server (for POP3, uidl is recommended)
flush | -F |  | Flush all seen messages before querying (DANGEROUS)
limitflush |  |  | Flush all oversized messages before querying
fetchall | -a |  | Fetch all messages whether seen or not
rewrite |  |  | Rewrite destination addresses for reply (default)
stripcr |  |  | Strip carriage returns from ends of lines
forcecr |  |  | Force carriage returns at ends of lines
pass8bits |  |  | Force BODY=8BITMIME to ESMTP listener
dropstatus |  |  | Strip Status and X -Mozilla-Status lines out of incoming mail
dropdelivered |  |  | Strip Delivered-To lines out of incoming mail
mimedecode |  |  | Convert q uoted-printable to 8-bit in MIME messages
idle |  |  | Idle waiting for new messages after each poll (IMAP only)
forceidle |  |  | Idle waiting for new messages after each poll (IMAP only, forced)
no keep | -K |  | Delete seen messages from server (default)
no flush |  |  | Do not flush all seen messages before querying (default)
no fetchall |  |  | Retrieve only new messages (default)
no rewrite |  |  | Do not rewrite headers
no stripcr |  |  | Do not strip carriage returns (default)
no forcecr |  |  | Do not force carriage returns at EOL (default)
no pass8bits |  |  | Do not force BODY=8BITMIME to ESMTP listener (default)
no dropstatus |  |  | Do not drop Status headers (default)
no dropdelivered |  |  | Do not drop Delivered-To headers (default)
no mimedecode |  |  | Do not convert q uoted-printable to 8-bit in MIME messages (default)
no idle |  |  | Do not idle waiting for new messages after each poll (IMAP only)
limit | -l |  | Set message size limit
warnings | -w |  | Set message size warning interval
batchlimit | -b |  | Max # messages to forward in single connect
fetchlimit | -B |  | Max # messages to fetch in single connect
fetchsizelimit |  |  | Max # message sizes to fetch in single transaction
fastuidl |  |  | Use binary search for first unseen message (POP3 only)
expunge | -e |  | Perform an expunge on every #th message (IMAP and POP3 only)
properties |  |  | String value is ignored by fetchmail (may be used by extension scripts)

All user options must begin with a user description (user or username option) and follow all server descriptions and options.

In the .fetchmailrc file, the 'envelope' string argument may be preceded by a whitespace-separated number. This number, if specified, is the number of such headers to skip over (that is, an argument of 1 selects the second header of the given type). This is sometimes useful for ignoring bogus envelope headers created by an ISP's local delivery agent or internal forwards (through mail inspection systems, for instance).

### Keywords Not Corresponding To Option Switches

The 'folder' and 'smtphost' options (unlike their command-line equivalents) can take a space- or comma-separated list of names following them.

All options correspond to the obvious command-line arguments, except the following: 'via', 'interval', 'aka', 'is', 'to', 'dns'/'no dns', 'checkalias'/'no checkalias', 'password', 'preconnect', 'postconnect', 'localdomains', 'stripcr'/'no stripcr', 'forcecr'/'no forcecr', 'pass8bits'/'no pass8bits' 'dropstatus/no dropstatus', 'dropdelivered/no dropdelivered', 'mimedecode/no mimedecode', 'no idle', and 'no envelope'.

The 'via' option is for if you want to have more than one configuration pointing at the same site. If it is present, the string argument will be taken as the actual DNS name of the mail server host to query. This will override the argument of poll, which can then simply be a distinct label for the configuration (e.g., what you would give on the command line to explicitly query this host).

The 'interval' option (which takes a numeric argument) allows you to poll a server less frequently than the basic poll interval. If you say 'interval N' the server this option is attached to will only be queried every N poll intervals.

### Singledrop versus Multidrop options

Please ensure you read the section titled THE USE AND ABUSE OF MULTIDROP MAILBOXES if you intend to use multidrop mode.

The 'is' or 'to' keywords associate the following local (client) name(s) (or server-name to client-name mappings separated by =) with the mail server user name in the entry. If an is/to list has '*' as its last name, unrecognized names are simply passed through. Note that until fetchmail version 6.3.4 inclusively, these lists could only contain local parts of user names (fetchmail would only look at the part before the @ sign). fetchmail versions 6.3.5 and newer support full addresses on the left hand side of these mappings, and they take precedence over any 'localdomains', 'aka', 'via' or similar mappings.

A single local name can be used to support redirecting your mail when your username on the client machine is different from your name on the mail server. When there is only a single local name, mail is forwarded to that local username regardless of the message's Received, To, Cc, and Bcc headers. In this case, fetchmail never does DNS lookups.

When there is more than one local name (or name mapping), fetchmail looks at the envelope header, if configured, and otherwise at the Received, To, Cc, and Bcc headers of retrieved mail (this is 'multidrop mode'). It looks for addresses with host name parts that match your poll name or your 'via', 'aka' or 'localdomains' options, and usually also for host name parts which DNS tells it are aliases of the mail server. See the discussion of 'dns', 'checkalias', 'localdomains', and 'aka' for details on how matching addresses are handled.

If fetchmail cannot match any mail server usernames or localdomain addresses, the mail will be bounced. Normally it will be bounced to the sender, but if the 'bouncemail' global option is off, the mail will go to the local postmaster instead. (see the 'postmaster' global option). See also BUGS.

The 'dns' option (normally on) controls the way addresses from multidrop mailboxes are checked. On, it enables logic to check each host address that does not match an 'aka' or 'localdomains' declaration by looking it up with DNS. When a mail server username is recognized attached to a matching host name part, its local mapping is added to the list of local recipients.

The 'checkalias' option (normally off) extends the lookups performed by the 'dns' keyword in multidrop mode, providing a way to cope with remote MTAs that identify themselves using their canonical name, while they are polled using an alias. When such a server is polled, checks to extract the envelope address fail, and fetchmail reverts to delivery using the To/Cc/Bcc headers (See below 'Header versus Envelope addresses'). Specifying this option instructs fetchmail to retrieve all the IP addresses associated with both the poll name and the name used by the remote MTA and to do a comparison of the IP addresses. This comes in handy in situations where the remote server undergoes frequent canonical name changes, that would otherwise require modifications to the rcfile. 'checkalias' has no effect if 'no dns' is specified in the rcfile.

The 'aka' option is for use with multidrop mailboxes. It allows you to pre-declare a list of DNS aliases for a server. This is an optimization hack that allows you to trade space for speed. When fetchmail, while processing a multidrop mailbox, grovels through message headers looking for names of the mail server, pre-declaring common ones can save it from having to do DNS lookups. Note: the names you give as arguments to 'aka' are matched as suffixes -- if you specify (say) 'aka netaxs.com', this will match not just a host name netaxs.com, but any host name that ends with '.netaxs.com'; such as (say) pop3.netaxs.com and mail.netaxs.com.

The 'localdomains' option allows you to declare a list of domains which fetchmail should consider local. When fetchmail is parsing address lines in multidrop modes, and a trailing segment of a host name matches a declared local domain, that address is passed through to the listener or MDA unaltered (local-name mappings are not applied).

If you are using 'localdomains', you may also need to specify 'no envelope', which disables fetchmail's normal attempt to deduce an envelope address from the Received line or X-Envelope-To header or whatever header has been previously set by 'envelope'. If you set 'no envelope' in the defaults entry it is possible to undo that in individual entries by using 'envelope <string>'. As a special case, 'envelope "Received"' restores the default parsing of Received lines.

The password option requires a string argument, which is the password to be used with the entry's server.

The 'preconnect' keyword allows you to specify a shell command to be executed just before each time fetchmail establishes a mail server connection. This may be useful if you are attempting to set up secure POP connections with the aid of ssh(1). If the command returns a nonzero status, the poll of that mail server will be aborted.

Similarly, the 'postconnect' keyword similarly allows you to specify a shell command to be executed just after each time a mail server connection is taken down.

The 'forcecr' option controls whether lines terminated by LF only are given CRLF termination before forwarding. Strictly speaking RFC821 requires this, but few MTAs enforce the requirement so this option is normally off (only one such MTA, qmail, is in significant use at time of writing).

The 'stripcr' option controls whether carriage returns are stripped out of retrieved mail before it is forwarded. It is normally not necessary to set this, because it defaults to 'on' (CR stripping enabled) when there is an MDA declared but 'off' (CR stripping disabled) when forwarding is via SMTP. If 'stripcr' and 'forcecr' are both on, 'stripcr' will override.

The 'pass8bits' option exists to cope with Microsoft mail programs that stupidly slap a "Content-Transfer-Encoding: 7bit" on everything. With this option off (the default) and such a header present, fetchmail declares BODY=7BIT to an ESMTP-capable listener; this causes problems for messages actually using 8-bit ISO or KOI-8 character sets, which will be garbled by having the high bits of all characters stripped. If 'pass8bits' is on, fetchmail is forced to declare BODY=8BITMIME to any ESMTP-capable listener. If the listener is 8-bit-clean (as all the major ones now are) the right thing will probably result.

The 'dropstatus' option controls whether nonempty Status and X-Mozilla-Status lines are retained in fetched mail (the default) or discarded. Retaining them allows your MUA to see what messages (if any) were marked seen on the server. On the other hand, it can confuse some new-mail notifiers, which assume that anything with a Status line in it has been seen. (Note: the empty Status lines inserted by some buggy POP servers are unconditionally discarded.)

The 'dropdelivered' option controls whether Delivered-To headers will be kept in fetched mail (the default) or discarded. These headers are added by qmail and Postfix mail servers in order to avoid mail loops but may get in your way if you try to "mirror" a mail server within the same domain. Use with caution.

The 'mimedecode' option controls whether MIME messages using the quoted-printable encoding are automatically converted into pure 8-bit data. If you are delivering mail to an ESMTP-capable, 8-bit-clean listener (that includes all of the major MTAs like sendmail), then this will automatically convert quoted-printable message headers and data into 8-bit data, making it easier to understand when reading mail. If your e-mail programs know how to deal with MIME messages, then this option is not needed. The mimedecode option is off by default, because doing RFC2047 conversion on headers throws away character-set information and can lead to bad results if the encoding of the headers differs from the body encoding.

The 'idle' option is intended to be used with IMAP servers supporting the RFC2177 IDLE command extension, but does not strictly require it. If it is enabled, and fetchmail detects that IDLE is supported, an IDLE will be issued at the end of each poll. This will tell the IMAP server to hold the connection open and notify the client when new mail is available. If IDLE is not supported, fetchmail will simulate it by periodically issuing NOOP. If you need to poll a link frequently, IDLE can save bandwidth by eliminating TCP/IP connects and LOGIN/LOGOUT sequences. On the other hand, an IDLE connection will eat almost all of your fetchmail's time, because it will never drop the connection and allow other polls to occur unless the server times out the IDLE. It also does not work with multiple folders; only the first folder will ever be polled.

The 'properties' option is an extension mechanism. It takes a string argument, which is ignored by fetchmail itself. The string argument may be used to store configuration information for scripts which require it. In particular, the output of '--configdump' option will make properties associated with a user entry readily available to a Python script.

### Miscellaneous Run Control Options

The words 'here' and 'there' have useful English-like significance. Normally 'user eric is esr' would mean that mail for the remote user 'eric' is to be delivered to 'esr', but you can make this clearer by saying 'user eric there is esr here', or reverse it by saying 'user esr here is eric there'

Legal protocol identifiers for use with the 'protocol' keyword are:

    auto (or AUTO) (legacy, to be removed from future release)
    pop2 (or POP2) (legacy, to be removed from future release)
    pop3 (or POP3)
    sdps (or SDPS)
    imap (or IMAP)
    apop (or APOP)
    kpop (or KPOP)

Legal authentication types are 'any', 'password', 'kerberos', 'kerberos_v4', 'kerberos_v5' and 'gssapi', 'cram-md5', 'otp', 'msn' (only for POP3), 'ntlm', 'implicit', 'external' (only IMAP). The 'password' type specifies authentication by normal transmission of a password (the password may be plain text or subject to protocol-specific encryption as in CRAM-MD5); 'kerberos' tells fetchmail to try to get a Kerberos ticket at the start of each query instead, and send an arbitrary string as the password; and 'gssapi' tells fetchmail to use GSSAPI authentication. See the description of the 'auth' keyword for more.

Specifying 'kpop' sets POP3 protocol over port 1109 with Kerberos V4 authentication. These defaults may be overridden by later options.

There are some global option statements: 'set logfile' followed by a string sets the same global specified by --logfile. A command-line --logfile option will override this. Note that --logfile is only effective if fetchmail detaches itself from the terminal and the logfile already exists before fetchmail is run, and it overrides --syslog in this case. Also, 'set daemon' sets the poll interval as --daemon does. This can be overridden by a command-line --daemon option; in particular --daemon 0 can be used to force foreground operation. The 'set postmaster' statement sets the address to which multidrop mail defaults if there are no local matches. Finally, 'set syslog' sends log messages to syslogd(8).

## DEBUGGING FETCHMAIL

### Fetchmail crashing

There are various ways in that fetchmail may "crash", i. e. stop operation suddenly and unexpectedly. A "crash" usually refers to an error condition that the software did not handle by itself. A well-known failure mode is the "segmentation fault" or "signal 11" or "SIGSEGV" or just "segfault" for short. These can be caused by hardware or by software problems. Software-induced segfaults can usually be reproduced easily and in the same place, whereas hardware-induced segfaults can go away if the computer is rebooted, or powered off for a few hours, and can happen in random locations even if you use the software the same way.

For solving hardware-induced segfaults, find the faulty component and repair or replace it. The Sig11 FAQ may help you with details.

For solving software-induced segfaults, the developers may need a "stack backtrace".

### Enabling fetchmail core dumps

By default, fetchmail suppresses core dumps as these might contain passwords and other sensitive information. For debugging fetchmail crashes, obtaining a "stack backtrace" from a core dump is often the quickest way to solve the problem, and when posting your problem on a mailing list, the developers may ask you for a "backtrace".

1. To get useful backtraces, fetchmail needs to be installed without getting stripped of its compilation symbols. Unfortunately, most binary packages that are installed are stripped, and core files from symbol-stripped programs are worthless. So you may need to recompile fetchmail. On many systems, you can type

    file `which fetchmail`

to find out if fetchmail was symbol-stripped or not. If yours was unstripped, fine, proceed, if it was stripped, you need to recompile the source code first. You do not usually need to install fetchmail in order to debug it.

2. The shell environment that starts fetchmail needs to enable core dumps. The key is the "maximum core (file) size" that can usually be configured with a tool named "limit" or "ulimit". See the documentation for your shell for details. In the popular bash shell, "ulimit -Sc unlimited" will allow the core dump.

3. You need to tell fetchmail, too, to allow core dumps. To do this, run fetchmail with the -d0 -v options. It is often easier to also add --nosyslog -N as well.

Finally, you need to reproduce the crash. You can just start fetchmail from the directory where you compiled it by typing ./fetchmail, so the complete command line will start with ./fetchmail -Nvd0 --nosyslog and perhaps list your other options.

After the crash, run your debugger to obtain the core dump. The debugger will often be GNU GDB, you can then type (adjust paths as necessary) gdb ./fetchmail fetchmail.core and then, after GDB has started up and read all its files, type backtrace full, save the output (copy & paste will do, the backtrace will be read by a human) and then type quit to leave gdb. Note: on some systems, the core files have different names, they might contain a number instead of the program name, or number and name, but it will usually have "core" as part of their name.

## INTERACTION WITH RFC 822

When trying to determine the originating address of a message, fetchmail looks through headers in the following order:

    Return-Path:
    Resent-Sender: (ignored if it does not contain an @ or !)
    Sender: (ignored if it does not contain an @ or !)
    Resent-From:
    From:
    Reply-To:
    Apparently-From:

The originating address is used for logging, and to set the MAIL FROM address when forwarding to SMTP. This order is intended to cope gracefully with receiving mailing list messages in multidrop mode. The intent is that if a local address does not exist, the bounce message will not be returned blindly to the author or to the list itself, but rather to the list manager (which is less annoying).

In multidrop mode, destination headers are processed as follows: First, fetchmail looks for the header specified by the 'envelope' option in order to determine the local recipient address. If the mail is addressed to more than one recipient, the Received line will not contain any information regarding recipient addresses.

Then fetchmail looks for the Resent-To:, Resent-Cc:, and Resent-Bcc: lines. If they exist, they should contain the final recipients and have precedence over their To:/Cc:/Bcc: counterparts. If the Resent-* lines do not exist, the To:, Cc:, Bcc: and Apparently-To: lines are looked for. (The presence of a Resent-To: is taken to imply that the person referred by the To: address has already received the original copy of the mail.)

## CONFIGURATION EXAMPLES

Note that although there are password declarations in a good many of the examples below, this is mainly for illustrative purposes. We recommend stashing account/password pairs in your $HOME/.netrc file, where they can be used not just by fetchmail but by ftp(1) and other programs.

The basic format is:

> poll SERVERNAME protocol PROTOCOL username NAME password PASSWORD

Example:

    poll pop.provider.net protocol pop3 username "jsmith" password "secret1"

Or, using some abbreviations:

    poll pop.provider.net proto pop3 user "jsmith" password "secret1"

Multiple servers may be listed:

    poll pop.provider.net proto pop3 user "jsmith" pass "secret1"
    poll other.provider.net proto pop2 user "John.Smith" pass "My^Hat"

Here is the same version with more whitespace and some noise words:

    poll pop.provider.net proto pop3
         user "jsmith", with password secret1, is "jsmith" here;
    poll other.provider.net proto pop2:
         user "John.Smith", with password "My^Hat", is "John.Smith" here;

If you need to include whitespace in a parameter string or start the latter with a number, enclose the string in double quotes. Thus:

    poll mail.provider.net with proto pop3:
         user "jsmith" there has password "4u but u cannot krak this"
         is jws here and wants mda "/bin/mail"

You may have an initial server description headed by the keyword 'defaults' instead of 'poll' followed by a name. Such a record is interpreted as defaults for all queries to use. It may be overwritten by individual server descriptions. So, you could write:

    defaults proto pop3
         user "jsmith"
    poll pop.provider.net
         pass "secret1"
    poll mail.provider.net
         user "jjsmith" there has password "secret2"

It is possible to specify more than one user per server. The 'user' keyword leads off a user description, and every user specification in a multi-user entry must include it. Here is an example:

    poll pop.provider.net proto pop3 port 3111
         user "jsmith" with pass "secret1" is "smith" here
         user jones with pass "secret2" is "jjones" here keep

This associates the local username 'smith' with the pop.provider.net username 'jsmith' and the local username 'jjones' with the pop.provider.net username 'jones'. Mail for 'jones' is kept on the server after download.

Here is what a simple retrieval configuration for a multidrop mailbox looks like:

    poll pop.provider.net:
         user maildrop with pass secret1 to golux 'hurkle'='happy' snark here

This says that the mailbox of account 'maildrop' on the server is a multidrop box, and that messages in it should be parsed for the server user names 'golux', 'hurkle', and 'snark'. It further specifies that 'golux' and 'snark' have the same name on the client as on the server, but mail for server user 'hurkle' should be delivered to client user 'happy'.

Note that fetchmail, until version 6.3.4, did NOT allow full user@domain specifications here, these would never match. Fetchmail 6.3.5 and newer support user@domain specifications on the left-hand side of a user mapping.

Here is an example of another kind of multidrop connection:

    poll pop.provider.net localdomains loonytoons.org toons.org
         envelope X-Envelope-To
         user maildrop with pass secret1 to * here

This also says that the mailbox of account 'maildrop' on the server is a multidrop box. It tells fetchmail that any address in the loonytoons.org or toons.org domains (including sub-domain addresses like 'joe@daffy.loonytoons.org') should be passed through to the local SMTP listener without modification. Be careful of mail loops if you do this!

Here is an example configuration using ssh and the plugin option. The queries are made directly on the stdin and stdout of imapd via ssh. Note that in this setup, IMAP authentication can be skipped.

    poll mailhost.net with proto imap:
         plugin "ssh %h /usr/sbin/imapd" auth implicit;
         user esr is esr here

## THE USE AND ABUSE OF MULTIDROP MAILBOXES

Use the multiple-local-recipients feature with caution -- it can bite. All multidrop features are ineffective in ETRN and ODMR modes.

Also, note that in multidrop mode duplicate mails may be suppressed. A piece of mail is considered duplicate if it does not have a discernible envelope recipient address, has the same header as the message immediately preceding and more than one addressee. Such runs of messages may be generated when copies of a message addressed to multiple users are delivered to a multidrop box. (To be precise, fetchmail 6.2.5 through 6.4.X use an MD5 hash of the raw message header, and only fetchmail 6.4.16+ document this properly. Fetchmail 5.0.8 (1999-09-14) through 6.2.4 used only the Message-ID header. 5.0.7 and older did not suppress duplicates.)

Note that this duplication killer code checking the entire header is very restrictive and may not suppress many duplicates in practice - for instance, if some X-Original-To or Delivered-To header differs. This is intentional and correct in such situations: wherever envelope information is available, it should be used for reliable delivery of mailing list and blind carbon copy (Bcc) messages. See the subsection Duplicate suppression below for suggestions.

### Header versus Envelope addresses

The fundamental problem is that by having your mail server toss several peoples' mail in a single maildrop box, you may have thrown away potentially vital information about who each piece of mail was actually addressed to (the 'envelope address', as opposed to the header addresses in the RFC822 To/Cc headers - the Bcc is not available at the receiving end). This 'envelope address' is the address you need in order to reroute mail properly.

Sometimes fetchmail can deduce the envelope address. If the mail server MTA is sendmail and the item of mail had just one recipient, the MTA will have written a 'by/for' clause that gives the envelope addressee into its Received header. But this does not work reliably for other MTAs, nor if there is more than one recipient. By default, fetchmail looks for envelope addresses in these lines; you can restore this default with -E "Received" or 'envelope Received'.

As a better alternative, some SMTP listeners and/or mail servers insert a header in each message containing a copy of the envelope addresses. This header (when it exists) is often 'X-Original-To', 'Delivered-To' or 'X-Envelope-To'. Fetchmail's assumption about this can be changed with the -E or 'envelope' option. Note that writing an envelope header of this kind exposes the names of recipients (including blind-copy recipients) to all receivers of the messages, so the upstream must store one copy of the message per recipient to avoid becoming a privacy problem.

Postfix, since version 2.0, writes an X-Original-To: header which contains a copy of the envelope as it was received.

Qmail and Postfix generally write a 'Delivered-To' header upon delivering the message to the mail spool and use it to avoid mail loops. Qmail virtual domains however will prefix the user name with a string that normally matches the user's domain. To remove this prefix you can use the -Q or 'qvirtual' option.

Sometimes, unfortunately, neither of these methods works. That is the point when you should contact your ISP and ask them to provide such an envelope header, and you should not use multidrop in this situation. When they all fail, fetchmail must fall back on the contents of To/Cc headers (Bcc headers are not available - see below) to try to determine recipient addressees -- and these are unreliable. In particular, mailing-list software often ships mail with only the list broadcast address in the To: header.

Note that a future version of fetchmail may remove To/Cc parsing!

When fetchmail cannot deduce a recipient address that is local, and the intended recipient address was anyone other than fetchmail's invoking user, mail will get lost. This is what makes the multidrop feature risky without proper envelope information.

A related problem is that when you blind-copy a mail message, the Bcc information is carried only as envelope address (it is removed from the headers by the sending mail server, so fetchmail can see it only if there is an X-Envelope-To header). Thus, blind-copying to someone who gets mail over a fetchmail multidrop link will fail unless the mail server host routinely writes X-Envelope-To or an equivalent header into messages in your maildrop.

In conclusion, mailing lists and Bcc'd mail can only work if the server you are fetching from

1. stores one copy of the message per recipient in your domain and

2. records the envelope information in a special header (X-Original-To, Delivered-To, X-Envelope-To).

### Good Ways To Use Multidrop Mailboxes

Multiple local names can be used to administer a mailing list from the client side of a fetchmail collection. Suppose your name is 'esr', and you want to both pick up your own mail and maintain a mailing list called (say) "fetchmail-friends", and you want to keep the alias list on your client machine.

On your server, you can alias 'fetchmail-friends' to 'esr'; then, in your .fetchmailrc, declare 'to esr fetchmail-friends here'. Then, when mail including 'fetchmail-friends' as a local address gets fetched, the list name will be appended to the list of recipients your SMTP listener sees. Therefore it will undergo alias expansion locally. Be sure to include 'esr' in the local alias expansion of fetchmail-friends, or you will never see mail sent only to the list. Also be sure that your listener has the "me-too" option set (sendmail's -oXm command-line option or OXm declaration) so your name is not removed from alias expansions in messages you send.

This trick is not without its problems, however. You will begin to see this when a message comes in that is addressed only to a mailing list you do not have declared as a local name. Each such message will feature an 'X-Fetchmail-Warning' header which is generated because fetchmail cannot find a valid local name in the recipient addresses. Such messages default (as was described above) to being sent to the local user running fetchmail, but the program has no way to know that this is actually the right thing.

### Bad Ways To Abuse Multidrop Mailboxes

Multidrop mailboxes and fetchmail serving multiple users in daemon mode do not mix. The problem, again, is mail from mailing lists, which typically does not have an individual recipient address on it. Unless fetchmail can deduce an envelope address, such mail will only go to the account running fetchmail (probably root). Also, blind-copied users are very likely never to see their mail at all.

If you are tempted to use fetchmail to retrieve mail for multiple users from a single mail drop via POP or IMAP, think again (and reread the section on header and envelope addresses above). It would be smarter to just let the mail sit in the mail server's queue and use fetchmail's ETRN or ODMR modes to trigger SMTP sends periodically (of course, this means you have to poll more frequently than the mail server's expiry period). If you cannot arrange this, try setting up a UUCP feed.

If you absolutely must use multidrop for this purpose, make sure your mail server writes an envelope-address header that fetchmail can see. Otherwise you will lose mail and it will come back to haunt you.

### Speeding Up Multidrop Checking

Normally, when multiple users are declared fetchmail extracts recipient addresses as described above and checks each host part with DNS to see if it is an alias of the mail server. If so, the name mappings described in the "to ... here" declaration are done and the mail locally delivered.

This is a convenient but also slow method. To speed it up, pre-declare mail server aliases with 'aka'; these are checked before DNS lookups are done. If you are certain your aka list contains all DNS aliases of the mail server (and all MX names pointing at it - note this may change in a future version) you can declare 'no dns' to suppress DNS lookups entirely and only match against the aka list.

### Duplicate suppression on multidrop

If fetchmail's duplicate suppression code does not kick in for your multidrop mail account, other options is using sieve, or for instance Courier's maildrop package (and in particular, its reformail program with the -D option) as the delivery agent (either from fetchmail, or from your local mail server that fetchmail injects into).

## SOCKS

Support for socks4/5 is a compile time configuration option. Once compiled in, fetchmail will always use the socks libraries and configuration on your system, there are no run-time switches in fetchmail - but you can still configure SOCKS: you can specify which SOCKS configuration file is used in the SOCKS_CONF environment variable.

For instance, if you wanted to bypass the SOCKS proxy altogether and have fetchmail connect directly, you could just pass SOCKS_CONF=/dev/null in the environment, for example (add your usual command line options - if any - to the end of this line):

    env SOCKS_CONF=/dev/null fetchmail

## EXIT CODES

To facilitate the use of fetchmail in shell scripts, an exit status code is returned to give an indication of what occurred during a given connection.

The exit codes returned by fetchmail are as follows:

0. One or more messages were successfully retrieved (or, if the -c option was selected, were found waiting but not retrieved).

1. There was no mail awaiting retrieval. (There may have been old mail still on the server but not selected for retrieval.) If you do not want "no mail" to be an error condition (for instance, for cron jobs), use a POSIX-compliant shell and add

    || [ $? -eq 1 ]

to the end of the fetchmail command line, note that this leaves 0 untouched, maps 1 to 0, and maps all other codes to 1. See also item #C8 in the FAQ.

2. An error was encountered when attempting to open a socket to retrieve mail. If you do not know what a socket is, do not worry about it -- just treat this as an 'unrecoverable error'. This error can also be because a protocol fetchmail wants to use is not listed in /etc/services.

3. The user authentication step failed. This usually means that a bad user-id, password, or APOP id was specified. Or it may mean that you tried to run fetchmail under circumstances where it did not have standard input attached to a terminal and could not prompt for a missing password.

4. Some sort of fatal protocol error was detected.

5. There was a syntax error in the arguments to fetchmail, or a pre- or post-connect command failed.

6. The run control file had bad permissions.

7. There was an error condition reported by the server. Can also fire if fetchmail timed out while waiting for the server.

8. Client-side exclusion error. This means fetchmail either found another copy of itself already running, or failed in such a way that it is not sure whether another copy is running.

9. The user authentication step failed because the server responded "lock busy". Try again after a brief pause! This error is not implemented for all protocols, nor for all servers. If not implemented for your server, "3" will be returned instead, see above. May be returned when talking to qpopper or other servers that can respond with "lock busy" or some similar text containing the word "lock".

10. The fetchmail run failed while trying to do an SMTP port open or transaction.

11. Fatal DNS error. Fetchmail encountered an error while performing a DNS lookup at startup and could not proceed.

12. BSMTP batch file could not be opened.

13. Poll terminated by a fetch limit (see the --fetchlimit option).

14. Server busy indication.

15. Internal error. You should see a message on standard error with details.

24 - 26, 28, 29

  These are internal codes and should not appear externally.

When fetchmail queries more than one host, return status is 0 if any query successfully retrieved mail. Otherwise the returned error status is that of the last host queried.

## FILES

~/.fetchmailrc, $HOME/.fetchmailrc, $HOME_ETC/.fetchmailrc, $FETCHMAILHOME/fetchmailrc

  default run control file (location can be overridden with environment variables)

~/.fetchids, $HOME/.fetchids, $HOME_ETC/.fetchids, $FETCHMAILHOME/.fetchids

  default location of file recording last message UIDs seen per host. (location can be overridden with environment variables)

~/.fetchmail.pid, $HOME/.fetchmail.pid, $HOME_ETC/.fetchmail.pid, $FETCHMAILHOME/fetchmail.pid

  default location of lock file (sometimes called pidfile or PID file, see option pidfile) to help prevent concurrent runs (non-root mode). (location can be overridden with environment variables)

~/.netrc, $HOME/.netrc, $HOME_ETC/.netrc

  your FTP run control file, which (if present) will be searched for passwords as a last resort before prompting for one interactively. (location can be overridden with environment variables)

/var/run/fetchmail.pid

  lock file (pidfile) to help prevent concurrent runs (root mode, Linux systems).

/etc/fetchmail.pid

  lock file (pidfile) to help prevent concurrent runs (root mode, systems without /var/run).

## ENVIRONMENT

Fetchmail's behavior can be altered by providing it with environment variables. Some may alter the operation of libraries that fetchmail links against, for instance, OpenSSL. Note that in daemon mode, you will need to quit the background daemon process and start a new fetchmail daemon for environment changes to take effect.

FETCHMAILHOME

  If this environment variable is set to a valid and existing directory name, fetchmail will read $FETCHMAILHOME/fetchmailrc (the dot is missing in this case), $FETCHMAILHOME/.fetchids (keeping its dot) and $FETCHMAILHOME/fetchmail.pid (without dot) rather than from the user's home directory. The .netrc file is always looked for in the invoking user's home directory (or $HOME_ETC) regardless of FETCHMAILHOME's setting.

FETCHMAILUSER

  If this environment variable is set, it is used as the name of the calling user (default local name) for purposes such as mailing error notifications. Otherwise, if either the LOGNAME or USER variable is correctly set (e.g., the corresponding UID matches the session user ID) then that name is used as the default local name. Otherwise getpwuid(3) must be able to retrieve a password entry for the session ID (this elaborate logic is designed to handle the case of multiple names per user ID gracefully).

FETCHMAIL_DISABLE_CBC_IV_COUNTERMEASURE

  (since v6.3.22): If this environment variable is set and not empty, fetchmail will disable a countermeasure against an SSL CBC IV attack (by setting SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS). This is a security risk, but may be necessary for connecting to certain non-standards-conforming servers. See fetchmail's NEWS file and fetchmail-SA-2012-01.txt for details. Earlier fetchmail versions (v6.3.21 and older) used to disable this countermeasure, but v6.3.22 no longer does that as a safety precaution.

FETCHMAIL_POP3_FORCE_RETR

  (since v6.3.9): If this environment variable is defined at all (even if empty), fetchmail will forgo the POP3 TOP command and always use RETR. This can be used as a workaround when TOP does not work properly.

FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS

  (since v6.3.17): If this environment variable is set and not empty, fetchmail will always load the default X.509 trusted certificate locations for SSL/TLS CA certificates, even if --sslcertfile and --sslcertpath are given. The latter locations take precedence over the system default locations. This is useful in case there are broken certificates in the system directories and the user has no administrator privileges to remedy the problem.

FETCHMAIL_WOLFSSL_DEBUG

  (since v6.4.25): If fetchmail is compiled and linked with wolfSSL, if wolfSSL was built with --enable-debug, and if this environment variable is set and not empty, then enable wolfSSL's debug mode. This will emit huge amounts of debug output to stderr.

HOME

  (documented since 6.4.1): This variable is normally set to the user's home directory. If it is set to a different directory than what is in the password database, HOME takes precedence.

HOME_ETC

  (documentation corrected to match behaviour of code since 6.4.1): If the HOME_ETC variable is set, it will override fetchmail's idea of $HOME, i. e. fetchmail will read .fetchmailrc, .fetchids, .fetchmail.pid and .netrc from $HOME_ETC instead of $HOME (or if HOME is also unset, from the passwd file's home directory location).

If HOME_ETC and FETCHMAILHOME are both set, FETCHMAILHOME takes precedence and HOME_ETC will be ignored.

SOCKS_CONF

  (only if SOCKS support is compiled in) this variable is used by the socks library to find out which configuration file it should read. Set this to /dev/null to bypass the SOCKS proxy.

SSL_CERT_DIR

  (with truly OpenSSL 3.0 compatible library): overrides OpenSSL's idea of the default trust directory or path (which contains individual certificate files and hashed symlinks), see the SSL_CTX_set_default_verify_paths(3) manual page for details, it may be in the openssl development package. If using another library's OpenSSL compatibility interface, this may not work. Since this variable only specifies a default value, the option --sslcertpath takes precedence if given.

SSL_CERT_FILE

  (with truly OpenSSL 3.0 compatible library): overrides OpenSSL's idea of the default trust certificate bundle file (which contains a concatenation of base64-encoded certificates in PEM format), see the SSL_CTX_set_default_verify_paths(3) manual page for details, it may be in the openssl development package. If using another library's OpenSSL compatibility interface, this may not work. Since this variable only specifies a default value, the option --sslcertfile takes precedence if given.

other system default variables

  such as TZ or the locale LC_XXX variables, will also influence program behaviour.

## SIGNALS

If a fetchmail daemon is running as root, SIGUSR1 wakes it up from its sleep phase and forces a poll of all non-skipped servers. For compatibility reasons, SIGHUP can also be used in 6.3.X but may not be available in future fetchmail versions.

If fetchmail is running in daemon mode as non-root, use SIGUSR1 to wake it (this is so SIGHUP due to logout can retain the default action of killing it).

Running fetchmail in foreground while a background fetchmail is running will do whichever of these is appropriate to wake it up.

## BUGS, LIMITATIONS, AND KNOWN PROBLEMS

Please check the NEWS file that shipped with fetchmail for more known bugs than those listed here.

Fetchmail cannot handle user names that contain blanks after a "@" character, for instance "demonstr@ti on". These are rather uncommon and only hurt when using UID-based --keep setups, so the 6.X.Y versions of fetchmail will not be fixed.

Fetchmail cannot handle configurations where you have multiple accounts that use the same server name and the same login. Any user@server combination must be unique.

The assumptions that the DNS and in particular the checkalias options make are not often sustainable. For instance, it has become uncommon for an MX server to be a POP3 or IMAP server at the same time. Therefore the MX lookups may go away in a future release.

The mda and plugin options interact badly. In order to collect error status from the MDA, fetchmail has to change its normal signal handling so that dead plugin processes do not get reaped until the end of the poll cycle. This can cause resource starvation if too many zombies accumulate. So either do not deliver to a MDA using plugins or risk being overrun by an army of undead.

The --interface option does not support IPv6 and it is doubtful if it ever will, since there is no portable way to query interface IPv6 addresses.

The RFC822 address parser used in multidrop mode chokes on some @-addresses that are technically legal but bizarre. Strange uses of quoting and embedded comments are likely to confuse it.

In a message with multiple envelope headers, only the last one processed will be visible to fetchmail.

Use of some of these protocols requires that the program send unencrypted passwords over the TCP/IP connection to the mail server. This creates a risk that name/password pairs might be snaffled with a packet sniffer or more sophisticated monitoring software. Under Linux and FreeBSD, the --interface option can be used to restrict polling to availability of a specific interface device with a specific local or remote IP address, but snooping is still possible if (a) either host has a network device that can be opened in promiscuous mode, or (b) the intervening network link can be tapped. We recommend the use of ssh(1) tunnelling to not only shroud your passwords but encrypt the entire conversation.

Use of the %F or %T escapes in an mda option could open a security hole, because they pass text manipulable by an attacker to a shell command. Potential shell characters are replaced by '_' before execution. The hole is further reduced by the fact that fetchmail temporarily discards any set-uid privileges it may have while running the MDA. For maximum safety, however, do not use an mda command containing %F or %T when fetchmail is run from the root account itself.

Fetchmail's method of sending bounces due to errors or spam-blocking and spam bounces requires that port 25 of localhost be available for sending mail via SMTP.

If you modify ~/.fetchmailrc while a background instance is running and break the syntax, the background instance will die silently. Unfortunately, it cannot die noisily because we do not yet know whether syslog should be enabled. On some systems, fetchmail dies quietly even if there is no syntax error; this seems to have something to do with buggy terminal ioctl code in the kernel.

The -f - option (reading a configuration from stdin) is incompatible with the plugin option.

The 'principal' option only handles Kerberos IV, not V.

Interactively entered passwords are truncated after 63 characters. If you really need to use a longer password, you will have to use a configuration file.

A backslash as the last character of a configuration file will be flagged as a syntax error rather than ignored.

The BSMTP error handling is virtually nonexistent and may leave broken messages behind.

Send comments, bug reports, gripes, and the like to the fetchmail-devel list

An fetchmail FAQ (in HTML form) is available at the fetchmail home page, it should also accompany your installation.

## AUTHOR

Fetchmail is currently maintained by Matthias Andree and Rob Funk with major assistance from Sunil Shetye (for code) and Rob MacGregor (for the mailing lists).

Most of the code is from Eric S. Raymond. Too many other people to name here have contributed code and patches.

This program is descended from and replaces popclient, by Carl Harris; the internals have become quite different, but some of its interface design is directly traceable to that ancestral program.

This manual page has been improved by Matthias Andree, R. Hannes Beinert, and Héctor García.

## SEE ALSO

README, README.SSL, README.SSL-SERVER, The Fetchmail FAQ, mutt(1), elm(1), mail(1), sendmail(8), popd(8), imapd(8), netrc(5), the fetchmail home page, (alternative URI); the maildrop home page.

## APPLICABLE STANDARDS

Note that this list is just a collection of references and not a statement as to the actual protocol conformance or requirements in fetchmail.

SMTP/ESMTP:

  RFC 821, RFC 2821, RFC 1869, RFC 1652, RFC 1870, RFC 1983, RFC 1985, RFC 2554.

mail:

  RFC 822, RFC 2822, RFC 1123, RFC 1892, RFC 1894.

POP2:

  RFC 937

POP3:

  RFC 1081, RFC 1225, RFC 1460, RFC 1725, RFC 1734, RFC 1939, RFC 1957, RFC 2195, RFC 2449.

APOP:

  RFC 1939.

RPOP:

  RFC 1081, RFC 1225.

IMAP2/IMAP2BIS:

  RFC 1176, RFC 1732.

IMAP4/IMAP4rev1:

  RFC 1730, RFC 1731, RFC 1732, RFC 2060, RFC 2061, RFC 2195, RFC 2177, RFC 2683.

ETRN:

  RFC 1985.

ODMR/ATRN:

  RFC 2645.

OTP:

  RFC 1938.

LMTP:

  RFC 2033.

GSSAPI:

  RFC 1508, RFC 1734, Generic Security Service Application Program Interface (GSSAPI)/Kerberos/SimpleAuthentication and Security Layer (SASL) Service Names.

TLS:

  RFC 2595.