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GNU/Linux |
RedHat 5.2(Apollo) |
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fetchmail(1) |
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fetchmail − fetch mail from a POP, IMAP, or ETRN-capable server
fetchmail
[options] [mailserver...]
fetchmailconf
fetchmail is a mail-retrieval and forwarding utility; it fetches mail from remote mailservers 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 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, POP3, IMAP2bis, and IMAP4. It can also use the ESMTP ETRN extension. (The RFCs describing all these protocols are listed at the end of this document.)
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.
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. The mail will then be delivered locally via your system’s MDA (Mail Delivery Agent, usually sendmail(8) but your system may use a different one such as smail, mmdf, or qmail). All the delivery-control mechanisms (such as .forward files) normally available through your system MDA and local delivery agents will therefore work.
If the program fetchmailconf is available, it will assist you in setting up and editing a fetchmailrc configuration. It runs under X and requires that the language Python and the Tk toolkit 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.
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 don’t specify any servers on the command line, each server in your ~/.fetchmailrc file will be queried.
To facilitate the use of fetchmail In scripts, pipelines, etc., 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 insttead in sections on AUTHENTICATION and DAEMON MODE which follows.
General
Options
−V, --version
Displays the version information for your copy of fetchmail. No mail fetch is performed. Instead, for each server specified, all 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. 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 error 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 stderr. Overrides --silent.
Disposal
Options
−a, --all
(Keyword: fetchall) 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.
−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.
−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.
−F, --flush
POP3/IMAP only. Delete old (previously retrieved) messages from the mailserver before retrieving new messages. This option does not work with ETRN. Warning: if your local MTA hangs and fetchmail is aborted, the next time you run fetchmail, it will delete mail that was never delivered to you. What you probably want is the default setting: if you don’t specify ’-k’, then fetchmail will automatically delete messages after successful delivery.
Protocol and
Query Options
−p, −-protocol proto
(Keyword: proto[col]) Specify the protocol to used when communicating with the remote mailserver. If no protocol is specified, fetchmail will try each of the supported protocols in turn, terminating after any successful attempt. proto may be one of the following:
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POP2 |
Post Office Protocol 2 | ||
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POP3 |
Post Office Protocol 3 | ||
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APOP |
Use POP3 with MD5 authentication. | ||
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RPOP |
Use POP3 with RPOP authentication. | ||
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KPOP |
Use POP3 with Kerberos V4 authentication on port 1109. | ||
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SDPS |
Use POP3 with Demon Internet’s SDPS extensions. | ||
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IMAP |
IMAP2bis, IMAP4, or IMAP4rev1 (fetchmail autodetects their capabilities). |
IMAP-K4
IMAP4, or IMAP4rev1 (fetchmail autodetects their capabilities) with RFC 1731 Kerberos v4 authentication.
IMAP-GSS
IMAP4, or IMAP4rev1 (fetchmail autodetects their capabilities) with RFC 1731 GSSAPI authentication.
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ETRN |
Use the ESMTP ETRN option. |
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. 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.
−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 RFC1725). Use with ’keep’ to use a mailbox as a baby news drop for a group of users.
−P, --port
(Keyword: port) The option permits you to specify a TCP/IP port to connect on. This option will seldom be necessary as all the supported protocols have well-established default port numbers.
−r folder, --folder folder
(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 or ETRN.
Delivery
Control Options
−S host, --smtphost host
(Keyword: smtp[host]) Specify a hunt list of hosts to forward mail to (one or more hostnames, comma-separated). In ETRN mode, set the host that the mailserver is asked to ship mail to. Hosts are tried in list order; the first one that is up becomes the forwarding or ETRN target for the current run. In ETRN mode, the FQDN of the machine running fetchmail is added to the end of the list as an invisible default; in all other modes ’localhost’ is added to the end of the list as an invisible default. Each hostname may have a ’/’-delimited suffix specifying a port or service to forward to; the default is 25 (or "smtp" under IPv6).
−D domain, --smtpaddress domain
(Keyword: smtpaddress) Specify the domain to be put in RCPT TO lines shipped to SMTP. The name of the SMTP server (as specified by --smtphost, or defaulted to "localhost") is used when this is not specified.
−Z nnn, --antispam nnn[,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, −-mda
(Keyword: mda) You can force mail to be passed to an MDA directly (rather than forwarded to port 25) with the -mda or -m option. If fetchmail is running as root, it sets its userid to that of the target user while delivering mail through an MDA. Some possible MDAs are "/usr/sbin/sendmail -oem", "/usr/lib/sendmail -oem", "/usr/bin/formail", and "/usr/bin/deliver". 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 use an MDA invocation like "sendmail -oem -t" that dispatches on the contents of To/Cc/Bcc, it will create mail loops and bring the just wrath of many postmasters down upon your head.
Resource
Limit Control Options
−l, --limit
(Keyword: limit) Takes a maximum octet size argument. Messages larger than this size will not be fetched, not be marked seen, and will be left on the server (in foreground sessions, the progress messages will note that they are "oversized"). 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 in interactive mode. It may not be used with daemon mode, as users would never receive a notification that messages were waiting. This option does not work with ETRN.
-b, --batchlimit
(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 qmail(8) and smail(8) may wait till the delivery socket is shut down to deliver. This may produce annoying delays when fetchmail(8) is processing very large batches. Setting the batch limit to some nonzero size will prevent these delays. This option does not work with ETRN.
-B, --fetchlimit
(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.
-e, --expunge
(keyword: expunge) When talking to an IMAP server, 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. 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, POP2, or POP3.
Authentication
Options
−u 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 IP 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.
−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. This option is currently only supported under Linux.
−A, --auth
(Keyword: auth[enticate]) This option permits you to specify a preauthentication type (see USER AUTHENTICATION below for details). The possible values are ’password’, ’kerberos_v5’ and ’kerberos’ (or, for excruciating exactness, ’kerberos_v4’). This option is provided primarily for developers; choosing KPOP protocol automatically selects Kerberos preauthentication, and all other alternatives use password authentication (though APOP uses a generated one-time key as the password and IMAP-K4 uses RFC1731 Kerberos v4 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. Unless the --version option is also on, the file must have permissions no more open than 0600 (u=rw,g=,o=) or else be /dev/null.
−i pathname, --idfile pathname
(Keyword: idfile) Specify an alternate name for the .fetchids file used to save POP3 UIDs.
−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, the rewrite option is ineffective.
-E, --envelope
(Keyword: envelope) This option changes the header fetchmail assumes will carry a copy of the mail’s envelope address. Normally this is ’X-Envelope-To’ but as this header is not standard, 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, and it should not be necessary unless you have globally disabled Received parsing with ’no envelope’ in the .fetchmailrc file.
-Q, --qvirtual
(Keyword: qvirtual) 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.userdom.dom.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 written in Python.
Every mode except ETRN requires authentication of the client. 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 mailserver.
If the mailserver 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 mailserver 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.
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. See the ftp(1) man page for details of the syntax of the .netrc file. (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.
Early versions of POP3 (RFC1081, RFC1225) supported a crude form of independent authentication using the rhosts file on the mailserver 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. 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 (the program to do this with on the server is probably called popauth(8)). You put the same password in your .fetchmailrc file. Each time fetchmail logs in, it sends a cryptographically secure hash of your password and the server greeting time to the server, which can verify it by checking its authorization database.
If your fetchmail was built with Kerberos support and you specify Kerberos preauthentication (either with --auth or the .fetchmailrc option authenticate kerberos_v4) it will try to get a Kerberos ticket from the mailserver at the start of each query.
If you use IMAP-K4, fetchmail will expect the IMAP server to have RFC1731-conformant AUTHENTICATE KERBEROS_V4 capability, and will use it.
If you use IMAP-GSS, fetchmail will expect the IMAP server to have RFC1731-conformant AUTHENTICATE GSSAPI capability, and will use it. Currently this has only been tested over Kerberos V, so you’re 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 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 (similar to APOP) is supported. If you are using POP3, and the RPA code has been compiled into your binary, and you query a server in the Compuserve csi.com domain, fetchmail will try to perform an RPA pass-phrase authentication instead of sending over the password en clair.
If you are using IPsec, the -T (--netsec) option can be used to pass an IP security request to be used when outgoing IP connections are initialized. You can also do this using the ’netsec’ server option in the .fetchmailrc file. In either case, the option value is a string in the format accepted by the net_security_strtorequest() function of the inet6_apps library.
The --daemon or -d option runs fetchmail in daemon mode. You must specify a numeric argument which is a polling interval in seconds.
In daemon mode, fetchmail puts itself in background and runs forever, querying each specified host and then sleeping for the given polling interval.
Simply invoking
fetchmail -d 900
will, therefore, poll all the hosts described in your ~/.fetchmailrc file (except those explicitly excluded with the ’skip’ verb) once every fifteen minutes.
It is 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 makes a per-user lockfile to guarantee this.
Normally, calling fetchmail with a daemon in the background sends a wakeup signal to the daemon, forcing it to poll mailservers immediately. (The wakeup signal is SIGHUP if fetchmail is running as root, SIGUSR1 otherwise.)
The option --quit will kill a running daemon process instead of waking it up (if there is no such option, fetchmail notifies you). If the --quit option is the only command-line option, that’s all there is to it.
The quit option may also be mixed with other command-line options; its effect is to kill any running daemon before doing what the other options specify in combination with the rc file.
The -t or --timeout option (keyword: timeout) 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 hang up on it. Without such a timeout fetchmail might hang up indefinitely trying to fetch mail from a down host. This would be particularly annoying for a fetchmail running in background. There is a default timeout which fetchmail -V will report.
The -L or --logfile option (keyword: set logfile) allows you to redirect status messages emitted while detached 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.
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 the specified log file if the The --nosyslog option turns off use of syslog(3), assuming it’s turned on in the .fetchmailrc file. -L or --logfile option was used.
The −N or --nodetach option suppresses backgrounding and detachment of the daemon process from its control terminal. This is primarily useful for debugging. 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.)
The --postmaster 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. Normally this is just the user who invoked fetchmail. If the invoking user is root, then the default of this option is the user ’postmaster’.
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 mailserver host.
The protocols fetchmail uses to talk to mailservers 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 has acknowledged to fetchmail that the message has been accepted for delivery. When forwarding to an MDA, however, there is more possibility of error (because there’s no way for fetchmail to get a reliable positive acknowledgement from the MDA).
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’ve already read on the server are being fetched (and deleted) even when you don’t specify --all. There are several reasons this can happen.
One could be that you’re 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.
Under POP3, blame RFC1725. That version of the POP3 protocol specification removed the LAST command, and some POP servers follow it (you can verify this by invoking fetchmail -v to the mailserver and watching the response to LAST early in the query). The fetchmail code tries to compensate by using POP3’s UID feature, storing the identifiers of messages seen in each session until the next session, in the .fetchids file. But this doesn’t track messages seen with other clients, or read directly with a mailer on the host but not deleted afterward. A better solution would be to switch to IMAP.
Another 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. The only real fix for this problem is to switch to IMAP.
The IMAP code uses the presence or absence of the server flag \Seen to decide whether or not a message is new. 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’s not specified by the IMAP RFCs. If you ever trip over a server that doesn’t, 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 mode, 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.
Many SMTP listeners allow administrators to set up ’spam filters’ that block unsolicited email from specified domains. A MAIL FROM 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. This return value is blessed by RFC1893 as "Delivery not authorized, message refused".
According to current drafts of the replacement for RFC821, 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].").
The exim MTA returns 501 "Syntax error in parameters or arguments", but will move to 550 soon.
The fetchmail code recognizes and discards the message on any of a list of responses that defaults to [571, 550, 501] but can be set with the ’antispam’ option. This is the only circumstance under which fetchmail ever discards mail.
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 won’t pay for downloading spam message bodies.
The preferred way to set up fetchmail is to write a .fetchmailrc file in your home directory. 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, when --version is not on your ~/.fetchmailrc may not have more than 0600 (u=rw,g=,o=) permissions; fetchmail will complain and exit otherwise.
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). 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 standard C-style escapes (\n, \t, \b, octal, and hex) to embed non-printable characters or string delimiters in strings.
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 descriptions. Note: the most common cause of syntax errors is mixing up user and server options.
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 server options. Keyword suffixes enclosed
in square brackets are optional. Those corresponding to
command-line options are followed by ’-’ and the
appropriate option letter.
Here are the legal user options:
Remember that all user options must follow all server 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 (that is, an argument of 1 selects the second header of the given type). This is sometime useful for ignoring bogus Received headers created by an ISP’s local delivery agent.
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’, ’mimedecode/no mimedecode’, and ’no envelope’.
The ’via’ option is for use with ssh, or 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). If the ’via’ name is ’localhost’, the poll name will also still be used as a possible match in multidrop mode; otherwise the ’via’ name will be used instead and the poll name will be purely a label.
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.
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.
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) the fetchmail code does look 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 default recipient is the value of the ’postmaster’ global option if that has been set; otherwise it’s the calling user (as set by the USER or LOGNAME variable in the environment).
The ’dns’ option (normally on) controls the way addresses from multidrop mailboxes are checked. On, it enables logic to check each host address that doesn’t 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.
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 ’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 programs 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.
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)
pop2 (or POP2)
pop3 (or POP3)
imap (or IMAP)
imap-k4 (or IMAP-K4)
imap-gss (or IMAP-GSS)
apop (or APOP)
kpop (or KPOP)
Legal authentication types are ’password’ or ’kerberos’. The former specifies authentication by normal transmission of a password (the password may be plaintext or subject to protocol-specific encryption as in APOP); the second tells fetchmail to try to get a Kerberos ticket at the start of each query instead, and send an arbitrary string as the password.
Specifying ’kpop’ sets POP3 protocol over port 1109 with Kerberos V4 preauthentication. These defaults may be overridden by later options.
There are currently three global option statements; ’set logfile’ followed by a string sets the same global specified by --logfile. A command-line --logfile option will override this. 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. Finally, ’set syslog’ sends log messages to syslogd(8).
When trying to detertmine the originating address of a message, fetchmail looks through headers in the following order:
Return-Path:
Resent-Sender:
Sender:
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 doesn’t exist, the bounce message won’t 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 Received: header (or whichever one is specified by the ’envelope’ option) to determine the local recipient adress. If the mail is addressed to more than one recipient, the Received line won’t contain any information regarding recipient adresses.
Then fetchmail looks for the Resent-To:, Resent-Cc:, and Resent-Bcc: lines. If they exists, they should contain the final recipients and have precedence over their To:/Cc:/Bcc: counterparts. If the Resent-* lines doesn’t exist, the To:, Cc:, Bcc: and Apparently-To: lines are looked for. (The presence of a Resent-To: is taken to impluy that the person referred by the To: address has already received the original copy of the mail).
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’s a version of those two 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;
This version is much easier to read and doesn’t cost significantly more (parsing is done only once, at startup time).
If you need to include whitespace in a parameter string, enclose the string in double quotes. Thus:
poll
mail.provider.net with proto pop3:
user jsmith there has password "u can’t 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’s possible to specify more than one user per server (this is only likely to be useful when running fetchmail in daemon mode as root). The ’user’ keyword leads off a user description, and every user specification in a multi-user entry must include it. Here’s 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
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’.
Here’s what a simple retrieval configuration for a multi-drop 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 multi-drop 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’.
Here’s an example of another kind of multidrop connection:
poll
pop.provider.net localdomains loonytoons.org:
user maildrop with pass secret1 to esr * here
This also says that the mailbox of account ’maildrop’ on the server is a multi-drop box. It tells fetchmail that any address in the loonytoons.org domain (including subdomain 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’s an example configuration using ssh. The queries go through an ssh connecting local port 1234 to port 110 on mailhost.net; the preconnect command sets up the ssh.
poll
mailhost.net via localhost port 1234 with proto pop3:
preconnect "ssh -f -L 1234:mailhost.net:110
|
mailhost.net sleep 20 </dev/null >/dev/null"; |
Use the multiple-local-recipients feature with caution -- it can bite. Also note that all multidrop features are ineffective in ETRN mode.
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/Bcc headers). 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’.
Alternatively, 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-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 recopients) to all receivers of the messages; it is therefore regarded by some administrators as a security/privacy problem.
A slight variation of the ’X-Envelope-To’ header is the ’Delivered-To’ put by qmail to avoid mail loops. It will probably 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. When they all fail, fetchmail must fall back on the contents of To/Cc/Bcc headers to try to determine recipient addressees -- and these are not reliable. In particular, mailing-list software often ships mail with only the list broadcast address in the To header.
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.
A related problem is that when you blind-copy a mail message, the Bcc information is carried only as envelope address (it’s not put in the headers fetchmail can see unless there is an X-Envelope header). Thus, blind-copying to someone who gets mail over a fetchmail link will fail unless the the mailserver host routinely writes X-Envelope or an equivalent header into messages in your maildrop.
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 mode 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 user 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 the safest but also slowest 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) you can declare ’no dns’ to suppress DNS lookups entirely and only match against the aka list.
To facilitate the use of fetchmail in shell scripts, an exit 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. | ||
|
1 |
There was no mail awaiting retrieval. (There may have been old mail still on the server but not selected for retrieval.) | ||
|
2 |
An error was encountered when attempting to open a socket for the POP connection. If you don’t know what a socket is, don’t worry about it -- just treat this as an ’unrecoverable error’. | ||
|
3 |
The user authentication step failed. This usually means that a bad user-id, password, or APOP id was specified. | ||
|
4 |
Some sort of fatal protocol error was detected. | ||
|
5 |
There was a syntax error in the arguments to fetchmail. | ||
|
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 isn’t 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 |
Internal error. You should see a message on standard error with details. |
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.
Eric S. Raymond <esr@snark.thyrsus.com>. This program is descended from and replaces popclient, by Carl Harris <ceharris@mal.com>; the internals are quite different, but some of its interface design is directly traceable to that ancestral program.
~/.fetchmailrc
default run control file
~/.fetchids
default location of file associating hosts with last message IDs seen (used only with newer RFC1725-compliant POP3 servers supporting the UIDL command).
~/.netrc
your FTP run control file, which (if present) will be searched for passwords as a last resort before prompting for one interactively.
~/.fetchmail.pid
lock file to help prevent concurrent runs (non-root mode).
/var/run/fetchmail.pid
lock file to help prevent concurrent runs (root mode, Linux systems).
/etc/fetchmail.pid
lock file to help prevent concurrent runs (root mode, systems without /var/run).
For correct initialization, fetchmail requires either that both the USER and HOME environment variables are correctly set, or that getpwuid(3) be able to retrieve a password entry from your user ID.
If a fetchmail daemon is running as root, SIGHUP wakes it up from its sleep phase and forces a poll of all non-skipped servers (this is in accordance with the usual conventions for system daemons).
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.
Enabling the ’mimedecode’ option (which defaults to off) may render invalid any PGP signatures attached to mail with quoted-printable headers. This bug will be fixed in a future version.
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.
Use of any of the supported protocols other than POP3 with OTP or RPA, APOP, KPOP, IMAP-K4, IMAP-GSS, or ETRN requires that the program send unencrypted passwords over the TCP/IP connection to the mailserver. This creates a risk that name/password pairs might be snaffled with a packet sniffer or more sophisticated monitoring software. Under Linux, the --interface option can be used to restrict polling to availability of a specific interface device with a specific local 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.
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 suid privileges it may have while running the MDA. For maximum safety, however, don’t use an mda command containing %F or %T when fetchmail is run from the root account itself.
Send comments, bug reports, gripes, and the like to Eric S. Raymond <esr@thyrsus.com>. An HTML FAQ is available at the fetchmail home page; surf to http://www.tuxedo.org/~esr/fetchmail or do a WWW search for pages with ’fetchmail’ in their titles.
elm(1), mail(1), sendmail(8), popd(8), imapd(8)
SMTP/ESMTP:
RFC 821, RFC 1869, RFC 1652, RFC 1870, RFC1983, RFC 1985
mail:
RFC 822
POP2:
RFC 937
POP3:
RFC 1081, RFC 1225, RFC 1460, RFC 1725, RFC 1939
APOP:
RFC 1460, RFC 1725, RFC 1939
RPOP:
RFC 1081, RFC 1225
IMAP2/IMAP2BIS:
RFC 1176, RFC 1732
IMAP4:
RFC 1730, RFC 1731, RFC 1732, RFC 2060, RFC 2061
ETRN:
RFC 1985
|
OTP: |
RFC 1938 |
|
fetchmail(1) | |