Provided by: dovecot-antispam_1.1+20090218.git.g28075fa-2_i386 bug

NAME

       antispam - The dovecot antispam plugin.

DESCRIPTION

       The  dovecot antispam plugin watches a defined spam folder (defaults to
       "SPAM"). It works together with a  spam  system  that  classifies  each
       message  as it is delivered. When the message is classified as spam, it
       shall be delivered to  the  spam  folder,  otherwise  via  the  regular
       filtering  file  the user may have (maildrop, sieve, ...). Now the user
       has  everything  classified  as  spam  in  the  special  spam   folder,
       everything else where it should be sorted to.

       This  is  not  enough  because  our  spam scanner needs training. We’ll
       occasionally have false positives and false negatives. Now this is  the
       point  where  the  dovecot  antispam plugin comes into play. Instead of
       moving mail into special folders or forwarding  them  to  special  mail
       addresses for retraining, the plugin offers two actions for the user:

        1. moving mail out of the SPAM folder and

        2. moving mail into the SPAM folder.

       The  dovecot  plugin  watches these actions (and additionally prohibits
       APPENDs to the SPAM folder, more for technical reasons than others) and
       tells  the  spam  classifier  that  it  made  an error and needs to re-
       classify the message (as spam/not spam depending on which  way  it  was
       moved.)

       The  advantage  of  this approach is that the mail ends up in the right
       target folder directly and needs not be touched twice.

       When other classifiers like crm114 that  have  an  ‘unsure’  state  are
       used, the plugin can also help, it supports an ‘unsure’ folder feature.
       The unsure folder cannot be written to, but moving out from there  into
       a folder that is considered a spam folder will learn as spam, any other
       folder (except trashes) will cause learning as not-spam.

INSTALLATION

       First copy the ‘defconfig’ file to ‘.config’ and edit it as  necessary.
       You  need  to  have  the  dovecot  headers installed and possibly other
       things depending on the backend you choose.  Then,  assuming  you  have
       configured the INSTALLDIR correctly, simply run ‘make install’.

       If  you  do  not wish to use the install target, simply copy the plugin
       (that is, the  file  lib90_antispam_plugin.so)  to  your  dovecot  imap
       plugin  directory; by default this is /usr/lib/dovecot/modules/imap/ or
       any dir you have configured (look for the mail_plugin_dir configuration
       directive.)

       Open       your      dovecot      configuration      file      (usually
       /etc/dovecot/dovecot.conf) and add the  antispam  plugin  to  the  imap
       protocol section:

       protocol imap {
           mail_plugins = antispam
           # mail_plugin_dir = /usr/lib/dovecot/modules/imap
       }

BACKENDS

       The  plugin supports multiple backends, there are currently two working
       backends included in the distribution:

   dspam executable backend (dspam specific)
       This backend instantly  retrains  by  calling  dspam.  There  are  some
       problems  with  this  approach  including  (1)  it can take a long time
       during which the IMAP session is blocked (2) when  many  users  retrain
       many messages at once server load may spike

   email sender backend (spam filter agnostic)
       This  backend sends mail to ham@example.com or spam@example.com (actual
       addresses are configurable) for retraining. This backend  can  be  very
       fast  to  set up if you already have a working setup that uses training
       addresses as recommended by many spam filter setups.

       Since this backend simply pipes the message to a  program  (by  default
       sendmail)  it can also be used for all kinds of other spam filters, for
       example spamassassin (by calling sa-learn instead of sendmail.)

   crm114 executable backend (crm114 specific)
       This backend instantly retrains by calling mailreaver.crm  which  needs
       to  be  configured  (defaulting to /bin/false!); the argument --good or
       --spam is given depending on how mail is moved.

       You need to use the unsure folder option (see below) together with this
       plugin  and deliver unsure mail into an unsure folder, spam mail into a
       spam folder and other mail regularly.

       Has the same drawbacks as the dspam-exec approach.

CONFIGURATION

       Aside from the build-configuration done in the ‘.config’ file, you have
       the following run-time options (shown along with the default):

       plugin {
           ##################
           # GENERIC OPTIONS

           # mail signature (used with any backend requiring a signature)
           antispam_signature = X-DSPAM-Signature

           # action to take on mails without signature
           # (used with any backend requiring a signature)
           # (we recommend only setting this to ’move’ after verifying that the
           # whole setup is working)
           # antispam_signature_missing = move # move silently without training
           antispam_signature_missing = error

           # semicolon-separated list of Trash folders (default unset i.e. none)
           # antispam_trash =
           # antispam_trash = trash;Trash;Deleted Items

           # semicolon-separated list of spam folders
           antispam_spam = SPAM

           # semicolon-separated list of unsure folders (default unset i.e. none)
           # antispam_unsure =

           # Whether to allow APPENDing to SPAM folders or not. Must be set to
           # "yes" (case insensitive) to be activated. Before activating, please
           # read the discussion below.
           # antispam_allow_append_to_spam = no

           ###########################
           # BACKEND SPECIFIC OPTIONS
           #

           #===================
           # dspam-exec plugin

           # dspam binary
           antispam_dspam_binary = /usr/bin/dspam

           # semicolon-separated list of extra arguments to dspam
           # (default unset i.e. none)
           # antispam_dspam_args =
           # antispam_dspam_args = --deliver=;--user;%u  # % expansion done by dovecot
           # antispam_dspam_args = --mode=teft

           # Ignore mails where the DSPAM result header contains any of the
           # strings listed in the blacklist
           # (default unset i.e. none)
           # antispam_dspam_result_header = X-DSPAM-Result
           # semicolon-separated list of blacklisted results, case insensitive
           # antispam_dspam_result_blacklist = Virus

           #=====================
           # mail sending plugin
           #
           # Because of the way this plugin works, you can also use it
           # to train via an arbitrary program that receives the message
           # on standard input, in that case you can use the config
           # options antispam_mail_spam and antispam_mail_notspam for
           # the argument that distinguishes between ham and spam.
           # For example:
           #   antispam_mail_sendmail = /path/to/mailtrain
           #   antispam_mail_sendmail_args = --for;%u
           #   antispam_mail_spam = --spam
           #   antispam_mail_notspam = --ham
           # will call it, for example, like this:
           #   /path/to/mailtrain --for jberg --spam

           # temporary directory
           antispam_mail_tmpdir = /tmp

           # spam/not-spam addresses (default unset which will give errors)
           # antispam_mail_spam =
           # antispam_mail_notspam =

           # sendmail binary
           antispam_mail_sendmail = /usr/sbin/sendmail
           #antispam_mail_sendmail_args = -f;%u@example.com # % expansion done by dovecot

           #===================
           # crm114-exec plugin

           # mailreaver binary
           antispam_crm_binary = /bin/false
           # antispam_crm_binary = /usr/share/crm114/mailreaver.crm

           # semicolon-separated list of extra arguments to dspam
           # (default unset i.e. none)
           # antispam_crm_args =
           # antispam_crm_args = --config=/path/to/config

           # NOTE: you need to set the signature for this backend
           antispam_signature = X-CRM114-CacheID
       }

ALLOWING APPENDS?

       You should be careful with allowing APPENDs to SPAM folders. The reason
       for possibly allowing it is to allow not-SPAM --> SPAM  transitions  to
       work  with  offlineimap. However, because with APPEND the plugin cannot
       know the source of the message, multiple bad scenarios can happen:

        1. SPAM --> SPAM transitions cannot be recognised and are trained

        2. the same holds for Trash --> SPAM transitions

       Additionally,  because  we   cannot   recognise   SPAM   -->   not-SPAM
       transitions, training good messages will never work with APPEND.

AUTHORS

       Johannes Berg, Frank Cusack, Benedikt Boehm, Andreas Schneider

                                15 October 2007                    ANTISPAM(7)