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

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.

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 stores 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 mailserver supports, and warn you of potential problems with that server.

General Options¶

-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-printables in passwords or other string names are shown as backslashed 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 doesn't play well with queries to multiple sites, and doesn't 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 can't 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 mailserver 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. Default to match historic fetchmail documentation, to 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 mailserver. 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 mailserver. Normally, messages are deleted from the folder on the mailserver after they have been retrieved. Specifying the keep option causes retrieved messages to remain in your folder on the mailserver. 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 mailserver. 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.

-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 mailserver 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 don't 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 mailserver 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 mailserver. If no protocol is specified, the default is AUTO. proto may be one of the following:

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 folder at a given time. 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.

-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.

--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 authentication.

-t <seconds> | --timeout <seconds>

(Keyword: timeout)
The timeout option allows you to set a server-nonresponse timeout in seconds. If a mailserver 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 it. 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 refetch 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 firewalling setup. The program will be looked up in $PATH and can optionally be passed the hostname 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 mailserver (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. Connect to the server using the specified base protocol over a connection secured by SSL. This option defeats opportunistic starttls negotiation. It is highly recommended to use --sslproto 'SSL3' --sslcertck to validate the certificates presented by the server and defeat the obsolete SSLv2 negotiation. More information is available in the README.SSL file that ships with fetchmail.

Note that fetchmail may still try to negotiate SSL through starttls even if this option is omitted. You can use the --sslproto option to defeat this behavior or tell fetchmail to negotiate a particular SSL protocol.

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).

--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 <name>

(Keyword: sslproto)
Forces an SSL/TLS protocol. Possible values are '', 'SSL2', 'SSL23', (use of these two values is discouraged and should only be used as a last resort) 'SSL3', and 'TLS1'. The default behaviour if this option is unset is: for connections without --ssl, use 'TLS1' that fetchmail will opportunistically try STARTTLS negotiation with TLS1. You can configure this option explicitly if the default handshake (TLS1 if --ssl is not used, does not work for your server.

Use this option with 'TLS1' value to enforce a STARTTLS connection. In this mode, it is highly recommended to also use --sslcertck (see below).

To defeat opportunistic TLSv1 negotiation when the server advertises STARTTLS or STLS, use ''. This option, even if the argument is the empty string, will also suppress the diagnostic 'SERVER: opportunistic upgrade to TLS.' message in verbose mode. The default is to try appropriate protocols depending on context.

--sslcertck

(Keyword: sslcertck)
Causes fetchmail to strictly check the server certificate against 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), the SSL connection will fail, regardless of the sslfingerprint option.

Note that CRL (certificate revocation lists) are only supported in OpenSSL 0.9.7 and newer! Your system clock should also be reasonably accurate when using this option.

Note that this optional behavior may become default behavior in future fetchmail versions.

--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/ subdirectory). Also, after OpenSSL upgrades, you may need to run c_rehash; particularly when upgrading from 0.9.X to 1.0.0.

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 hostname 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 can't be made to use proper certificates.

--sslfingerprint <fingerprint>

(Keyword: sslfingerprint)
Specify the fingerprint of the server key (an MD5 hash of the key) in hexadecimal notation with colons separating groups of two digits. The letter hex digits must be in upper case. This is the default format OpenSSL uses, and the one 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 needs to be obtained or verified over a secure channel, and certainly not over the same Internet connection that fetchmail would use.

Using this option will prevent printing certificate verification errors as long as --sslcertck is unset.

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

	openssl x509 -in cert.pem -noout -md5 -fingerprint

For details, see x509(1ssl).

Delivery Control Options¶

-S <hosts> | --smtphost <hosts>

(Keyword: smtp[host])
Specify a hunt list of hosts to forward mail to (one or more hostnames, 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 hostname 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.

--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.

--smtpname <user@domain>

(Keyword: smtpname)
Specify the domain and user to be put in RCPT TO lines shipped to SMTP. The default user is the current local user.

-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.

-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 isn't 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 don't 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 accomodate 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 isn't 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 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 resending 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 mailserver. 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 mailserver via SLIP or PPP. That is a relatively secure channel. But when other TCP/IP routes to the mailserver 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 SGID 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 ssh. When any (the default) is specified, fetchmail tries first methods that don't require a password (EXTERNAL, GSSAPI, KERBEROS IV, KERBEROS 5); then it looks for methods that mask your password (CRAM-MD5, X-OTP - note that NTLM and MSN are not autoprobed for POP3 and MSN is only supported for POP3); and only if the server doesn't support any of those will it ship your password en clair. Other values may be used to force various authentication methods (ssh suppresses authentication and is thus useful for IMAP PREAUTH). (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 ssh when you are using an end-to-end secure connection such as an ssh tunnel; 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.

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. Default: see "ENVIRONMENT" below.

-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 mailserver hostname 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 mailserver 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 hostname 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.

Removed Options¶

-T | --netsec

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

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 mailserver 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. See the ftp(1) man page for details of the syntax of the ~/.netrc file. 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.

On mailservers 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 don't know the correct user-id and password for your mailbox account.

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.

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

Note that fetchmail currently uses the OpenSSL library, which is severely underdocumented, so failures may occur just because the programmers are not aware of OpenSSL's requirement of the day. For instance, since v6.3.16, fetchmail calls OpenSSL_add_all_algorithms(), which is necessary to support certificates with SHA256 on OpenSSL 0.9.8 -- this information is deeply hidden in the documentation and not at all obvious. Please do not hesitate to report subtle SSL failures.

You can access SSL encrypted services by specifying the --ssl option. You can also do this using the "ssl" user option in the .fetchmailrc file. With SSL encryption enabled, queries are initiated over a connection after negotiating an SSL session, and the connection fails if SSL cannot be negotiated. 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. The --sslproto 'SSL3' option should be used to select the SSLv3 protocol (default if unset: v2 or v3). Also, the --sslcertck command line or sslcertck run control file option should be used to force strict certificate checking - see below.

If SSL is not configured, fetchmail will usually opportunistically try to use STARTTLS. STARTTLS can be enforced by using --sslproto "TLS1". TLS 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 cleartest passwords. Use of the sslcertck or --sslcertck option is therefore advised.

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 doesn't help against an active attacker. It's 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 ). 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.

ESMTP AUTH¶

fetchmail also supports authentication to the ESMTP server on the client side according to RFC 2554. 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.

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 lockfile 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 aren't 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 --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 aren't 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).

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's turned on in the ~/.fetchmailrc file.

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 (though perhaps it shouldn't).

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 mailserver) but not delivered locally due to some transient error, it will be re-fetched during the next poll cycle. (The IMAP logic doesn't delete messages until they're 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.

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're ignored, but but can make entries much easier to read at a glance. The punctuation characters ':', ';' and ',' are also ignored.

Poll vs. 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:

Here are the legal server options:

Here are the legal user descriptions and options:

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 sometime 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 mailserver 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 vs. 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 mailserver 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 mailserver. 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 hostname parts that match your poll name or your 'via', 'aka' or 'localdomains' options, and usually also for hostname parts which DNS tells it are aliases of the mailserver. See the discussion of 'dns', 'checkalias', 'localdomains', and 'aka' for details on how matching addresses are handled.

If fetchmail cannot match any mailserver 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 mailserver username is recognized attached to a matching hostname 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're 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 vs. 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 mailserver, 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 hostname netaxs.com, but any hostname 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 mailserver 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 mailserver will be aborted.

Similarly, the 'postconnect' keyword similarly allows you to specify a shell command to be executed just after each time a mailserver 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 it 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 mailservers in order to avoid mail loops but may get in your way if you try to "mirror" a mailserver 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 doesn't 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', 'ssh', '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).

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. 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.

Header vs. Envelope addresses¶

The fundamental problem is that by having your mailserver 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 mailserver 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 doesn't 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's 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 the mailserver 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're 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'll 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 isn't removed from alias expansions in messages you send.

This trick is not without its problems, however. You'll 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 that's 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're 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 mailserver'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 mailserver's expiry period). If you can't arrange this, try setting up a UUCP feed.

If you absolutely must use multidrop for this purpose, make sure your mailserver 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's an alias of the mailserver. 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 mailserver aliases with 'aka'; these are checked before DNS lookups are done. If you're certain your aka list contains all DNS aliases of the mailserver (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.