Mail Server
From Briki
Contents
- 1 General
- 2 Switching from /var/mail/<user> to $HOME/Maildir
- 3 Postfix
- 4 SpamAssassin
- 5 Roundcube
- 6 Dovecot
General
See https://help.ubuntu.com/community/MailServer for an introduction to MTA/Spamassassin
- MTA
- Mail Transport Agent (generally SMTP)
- MDA
- Mail Delivery Agent
- MUA
- Mail User Agent (generally POP3 or IMAP)
Briefly, the workflow for mail delivery is:
[Internet] -> postfix (MTA) -> SpamAssassin -> postfix (MTA) -> procmail (MDA) -> $HOME/Maildir
and for mail viewing:
$HOME/Maildir -> Courier (IMAP MUA) -> Thunderbird/Outlook
or
$HOME/Maildir -> Mutt/Pine
Switching from /var/mail/<user> to $HOME/Maildir
- Add to /etc/procmailrc:
# Ensure mail files are owned by recipient DROPPRIVS=yes MAILDIR=$HOME/Maildir DEFAULT="$MAILDIR/"
- Change session optional pam_mail.so standard to session optional pam_mail.so standard dir=~/Maildir in /etc/pam.d/login (to set $MAIL and get new mail prompts in bash)
- Change session optional pam_mail.so standard noenv # [1] to session optional pam_mail.so standard dir=~/Maildir # [1] in /etc/pam.d/ssh (to set $MAIL and get new mail prompts in bash)
- Change session optional pam_mail.so nopen to session optional pam_mail.so nopen dir=~/Maildir in /etc/pam.d/su (to set $MAIL but suppress new mail prompts in bash for superuser)
- Change MAIL_DIR /var/mail to MAIL_DIR Maildir/ in /etc/login.defs (this is only used for creating/deleting the mail folder when users are added or deleted; also, some reports suggest QMAIL_DIR Maildir/ is the correct setting, but this isn't mentioned in the login.defs man page)
- Create ~/.muttrc with the contents:
set mbox_type=Maildir # Set locations of the common folders set folder="~/Maildir" set mask="!^\\.[^.]" set mbox="~/Maildir" set record="+.Sent" set postponed="+.Drafts" set spoolfile="~/Maildir" # Set up mailboxes by scanning for all subfolders in ~/Maildir mailboxes `echo -n "+ "; find ~/Maildir -type d -name ".*" -printf "+'%f' "` # Add macros to make the folder browser usable by always using the mailboxes setup above macro index c "<change-folder>?<toggle-mailboxes>" "open a different folder" macro pager c "<change-folder>?<toggle-mailboxes>" "open a different folder" # Go straight to the folder browser when copying, moving and attaching mail macro index C "<copy-message>?<toggle-mailboxes>" "copy a message to a mailbox" macro index M "<save-message>?<toggle-mailboxes>" "move a message to a mailbox" macro compose A "<attach-message>?<toggle-mailboxes>" "attach message(s) to this message"
NB: /usr/bin/mail will no longer work for viewing mails (it gives the error "/home/<user>/Maildir" is a directory). It's a pretty obtuse command for mail viewing anyway, however (and it will still work for sending mails from the cmd-line)
Postfix
Configuring SpamAssassin as a content filter
Adapted from: http://www.debuntu.org/postfix-and-pamassassin-how-to-filter-spam
Install and configure SpamAssassin
-
wajig install spamassassin spamc
- Create a spamd user:
sudo adduser --system --group --home /var/lib/spamassassin userid
- Create /var/run/spamassassin and /var/lib/spamassassin, owned by spamd:spamd
- Add/change the following lines in /etc/default/spamassassin:
ENABLED=1 OPTIONS="--create-prefs --max-children 5 --port 1783 -s /var/log/spamassassin/spamd.log" PIDFILE="/var/run/spamassassin/spamd.pid"
- Edit /etc/init.d/spamassassin:
- Add USER=spamd to the default variables block
- Add --chuid $USER to the start and restart cmds
Configure postfix
- Add to /etc/postfix/master.cf:
spamassassin unix - n n - - pipe
user=spamd argv=/usr/bin/spamc -e
/usr/sbin/sendmail -oi -f ${sender} ${recipient}
Again in /etc/postfix/master.cf, change the smtp content filters to:
smtp inet n - - - - smtpd
-o content_filter=spamassassin
- Ensure postfix is set to deliver via procmail (see below)
Configure procmail
- Create /etc/procmailrc:
SHELL=/bin/sh LOGFILE=/var/log/procmail/$LOGNAME.log LOGABSTRACT=all VERBOSE=off # Ensure mail files are owned by recipient DROPPRIVS=yes MAILDIR=$HOME/Maildir DEFAULT="$MAILDIR/" SPAM="$MAILDIR/.Spam/" :0 * ^X-Spam-Status: Yes $SPAM
Note: DROPPRIVS line is only needed for systems where /usr/bin/procmail is suid root
Configuring postfix delivery method
The following config should be placed within /etc/postfix/main.cf
To use postfix's builtin MDA with mbox format (/var/spool/mail/$USER)
# Use mbox mailboxes (the default) home_mailbox = mbox
Ensure no mailbox_command is specified
To use postfix's builtin MDA with Maildir formar ($HOME/Maildir/*)
# Use Maildir style mailboxes home_mailbox = Maildir/
Ensure no mailbox_command is specified
To use procmail as external MDA
# Use procmail mailbox_command = /usr/bin/procmail
Ensure no home_mailbox is specified
Configuring mail for an unknown destination to route to a specific user
# Redirect unknown users to andrew luser_relay = andrew local_recipient_maps =
Hardening postfix
Add the following to /etc/postfix/main.cf:
## Restrictions # Require a valid handshake, with the sender announcing its name smtpd_helo_required = yes # Require the sending server to have an A or MX record in DNS #smtpd_sender_restrictions = hash:/etc/postfix/sender_access,reject_unknown_sender_domain smtpd_sender_restrictions = reject_unknown_sender_domain # Require the recipient to be a configured destination, unless from mynetworks (NB. This is default, anyway) smtpd_recipient_restrictions = permit_mynetworks, reject_unauth_destination
Emptying deferred queue
To attempt redelivery:
sudo postfix flush
To simply delete all deferred mails:
sudo postsuper -d ALL
Testing postfix header_checks
postmap -q - regexp:/etc/postfix/header_checks < /tmp/testmessage
Fixing 'mail for <host> loops back to myself'
- Ensure <host> is listed in mydestination in /etc/postfix/main.cf (you may need to add both the FDQN and the simple hostname)
SpamAssassin
Pyzor
Meaning of output like:
82.94.255.100:24441 (200, 'OK') 1206 0
- 82.94.255.100
- 24441
- Pyzor server
- (200, 'OK')
- HTTP response from server
- 1206
- Number of spam matches for tested message
- 0
- Number of whitelist (definite non-spam) matches for tested message
Pyzor will return 0 (identifying the message as spam) only if number of spam matches > 0 and number of whitelist matches = 0.
Roundcube
Fixing blank screen on IMAPS login with "Call to undefined function mcrypt_module_open" error in /var/log/roundcube/errors
- Install php-mcrypt
