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diff --git a/_posts/2016-10-31-freebsd-mailserver-part-5-filtering-mail.md b/_posts/2016-10-31-freebsd-mailserver-part-5-filtering-mail.md deleted file mode 100644 index d1797eb..0000000 --- a/_posts/2016-10-31-freebsd-mailserver-part-5-filtering-mail.md +++ /dev/null @@ -1,127 +0,0 @@ ---- -title: "FreeBSD email server - Part 5: Filtering mail" -date: 2016-10-31 20:02:19 -tags: Tutorial FreeBSD Email Postfix SpamAssassin Pigeonhole -layout: post ---- - -Being able to send mail and not be flagged as spam is pretty awesome on itself. -But you also get hit by a lot of spam. The more you give out your email address -and domain name, the more spam you will receive over time. I welcome you to -another part of the FreeBSD email server series. In this part, we will set up -email filtering at the server side. - -We will accomplish this with a couple packages, [SpamAssassin][spamassassin] -and [Pigeonhole][pigeonhole]. The former deals with scanning the emails to -deduce whether it is spam or not. The latter filters messages. We will use this -filtering to drop emails marked as spam by SpamAssassin into the Junk folder, -instead of the inbox. - -## Installing the packages -Both packages are available through FreeBSD's `pkg` utility. Install them as -such. - -{% highlight sh %} -pkg install dovecot-pigeonhole spamassassin -{% endhighlight %} - -## SpamAssassin -### Enabling the service -Like most services, you have to enable them as well. Pigeonhole is an extension -to Dovecot, and Dovecot will handle this one. SpamAssassin requires you to -configure the service as well. You can enable it and set sane configuration to -it with the following two commands. - -{% highlight sh %} -echo 'spamd_enable="YES"' >> /etc/rc.conf.local -echo 'spamd_flags="-u spamd -H /srv/mail"' >> /etc/rc.conf.local -{% endhighlight %} - -### Acquiring default spam rules -SpamAssassin has to "learn" what counts as *spam* and what counts as *ham*. To -fetch these rules, you should execute the updates for SpamAssassin with the -following command. - -{% highlight sh %} -sa-update -{% endhighlight %} - -You most likely want to run this once every while, so it is advised to setup a -cronjob for this purpose. - -## Postfix -In order to have mails checked by SpamAssassin, Postfix must be instructed to -pass all email through to SpamAssassin, which will hand them back with a -`X-Spam-Flag` header attached to them. This header can be used by other -applications to treat it as spam. - -### master.cf -There's not much to include to the already existing Postfix configuration to -enable SpamAssassin to do its job. Just open `/usr/local/etc/postfix/master.cf` -and append the block given below. - -{% highlight ini %} -spamassassin unix - n n - - pipe - user=spamd argv=/usr/local/bin/spamc - -f -e /usr/sbin/sendmail -oi -f ${sender} ${recipient} -{% endhighlight %} - -## Pigeonhole -Pigeonhole is an implementation of Sieve for Dovecot. It deals with filtering -messages on the server side using a set of rules, defined in a file usually -named `sieve`. This file is generally saved at -`/srv/mail/domain.tld/user/sieve`. A default file to filter spam out is the -following example. - -``` -require [ - "fileinto", - "mailbox" -]; - -if header :contains "X-Spam-Flag" "YES" { - fileinto :create "Junk"; - stop; -} -``` - -This looks for the `X-Spam-Flag` header, which is added by SpamAssassin. If it -is set to `YES`, this indicates SpamAssassin thinks the message is spam. As -such, sieve is instructed to filter this message into the folder `Junk`, and to -create this folder if it does not exist yet. The `stop;` makes sieve stop -trying to process this message further based on later rules. - -## Dovecot -Dovecot needs some additional configuration to work with Pigeonhole. Modify the -following files and add the contents described. - -### conf.d/20-lmtp.conf -This will enable Pigeonhole in Dovecot. - -{% highlight ini %} -protocol lmtp { - mail_plugins = $mail_plugins sieve -} -{% endhighlight %} - -### conf.d/90-plugin.conf -This configures Pigeonhole to look for a file named `sieve` in the mailbox -homedir, and execute that when delivering mail. - -{% highlight ini %} -plugin { - sieve = /srv/mail/%d/%n/sieve -} -{% endhighlight %} - -## Conclusion -Spam is a pain, especially if you get a lot of it. The configuration added in -this part of the FreeBSD email server series should get rid of most of it. This -also concludes the series. If you have any questions or suggestions, please -contact me via any of the methods detailed on [my home page][home]. - -Thanks for reading along, and enjoy your very own email server! - -[home]: {{ "/" | prepend: site.baseurl }} -[pigeonhole]: http://pigeonhole.dovecot.org/ -[spamassassin]: https://spamassassin.apache.org/ |