Sieve Mail Filtering Setup

This article covers:

1. Email filtering e.g. showing trash can to newsletters who do not honor unsubscribe links automatically. This is like Gmail filters.
2. Global spam filtering e.g. moving spam from inbox to junk folder (automatically)

Installing packages for sieve and managesieve

We are using dovecot pigeonhole project for sieve support.

apt-get install dovecot-sieve dovecot-managesieved

Please note that, installing sieve without spamassassin won’t filter spam messages automatically.

Sieve-Dovecot Configuration

Enable sieve plugin support for dovecot-lmtp

vim /etc/dovecot/conf.d/20-lmtp.conf

Add following:

protocol lmtp {
  postmaster_address = admin@example.com
  mail_plugins = $mail_plugins sieve
}

Edit sieve dovecot-pluign configuration

vim /etc/dovecot/conf.d/90-sieve.conf

Add following:

plugin {
   sieve = ~/.dovecot.sieve
   sieve_global_path = /var/lib/dovecot/sieve/default.sieve
   sieve_dir = ~/sieve
   sieve_global_dir = /var/lib/dovecot/sieve/
}

Restart Dovecot

Restart dovecot for changes to take effect:

service dovecot restart

You can see managesieve service running on port number 4190 by using telnet command:

telnet example.com 4190

Will output something like:

Trying 162.243.12.140...
Connected to test3.rtcamp.com.
Escape character is '^]'.
"IMPLEMENTATION" "Dovecot Pigeonhole"
"SIEVE" "fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date ihave"
"NOTIFY" "mailto"
"SASL" "PLAIN LOGIN"
"STARTTLS"
"VERSION" "1.0"
OK "Dovecot ready."

You can find sieve commands here which you can run inside telnet shell to manage sieve filters. Or you can use following method to manipulate global sieve rules directly.

Global Sieve Rules

You can use sieve to implement/enforce server-wise rules/organization policies.

Create global sieve rules file

mkdir /var/lib/dovecot/sieve/

Then create/open global sieve rules files:

vim /var/lib/dovecot/sieve/default.sieve

Following example rules moves spam emails from Inbox to Junk folder automatically. X-Spam-Flag is added by spamassassin and amavis.

require "fileinto";
if header :contains "X-Spam-Flag" "YES" {
  fileinto "Junk";
}

Change Ownership:

chown -R vmail:vmail /var/lib/dovecot

Compile sieve rules:

sievec /var/lib/dovecot/sieve/default.sieve

At this point you have sieve interpreter and managesieve service running.

Enabling sieve plugin in roundcube

Roundcube has 2 plugins for sieve:managesieve andsieverules.

Both provides similar functionality but I like support for extended mail-headers in UI provided by sieverules. So we will be using sieverules plugin.

Enable sieverules plugin in roundcube config

Open

vim /etc/roundcube/main.inc.php

Add sieverules to list of roundcube plugins

$rcmail_config['plugins'] = array('sieverules');

Configure sieverules plugin to use correct managesieve service port

Open

vim /etc/roundcube/plugins/sieverules/config.inc.php

Add/Update following line:

$rcmail_config['sieverules_port'] = 4190;

Testing

If you are using spamassasin, you can test global filters using this spam testing guide.