How To Enable Sieve Mail Filtering, including GUI rule editing

MrPete · December 7, 2021, 10:21pm

This is an updated set of instructions as of Dec 2021. My goals:

Don’t break Spamassassin/Procmail
Enable the use of (very efficient, powerful, and standards-based) Sieve filtering in Virtualmin
Enable some form of GUI filter editing if at all possible
And do it without draining the limited resources of the Virtualmin team

STEPS

1. Install

apt install dovecot-managesieved (This will auto-install dovecot-sieve)

2. Configuration files

1. /etc/dovecot/conf.d/15-lda.conf
Add sieve as a plugin. You may have others already. By default, the line to edit will now look like this

mail_plugins = $mail_plugins sieve

NOTE: try grep mail_plugins conf.d/ – If any other files have uncommented $mail_plugins lines, add sieve to those as well

2. /etc/dovecot/conf.d/20-managesieve.conf

This file is installed in step 1, but nothing is enabled. My changes involved:

# Uncomment to enable managesieve protocol:
protocols = $protocols sieve

Uncommenting the managesieve-login service (Important: there are FIVE required lines, incl one at the end of the block! The sample has a lot more; I made no other changes.)

service managesieve-login {
  inet_listener sieve {
    port = 4190
  }
}

Uncommenting the protocol sieve block (just the start and end-- I didn’t change anything else)

protocol sieve {
}

Add two lines to the end of /etc/procmailrc (you can do this in the webmin GUI if you like)

:0 w
/usr/lib/dovecot/deliver

NOTE: Depending on your linux distro, that path to the deliver app may be different

3. Verify

service dovecot restart
lsof -i:4190

The lsof should show listener(s) on sieve (4190) port

If you have firewalls, ensure port 4190 is enabled, just like other mail ports (25, 110, 465, 587, 993, 995)

4. Add Sieve GUI editor

Several mail clients support the Sieve Management protocol!
For my use case, I installed the Thunderbird client solely for sieve script viewing and editing. I don’t use Thunderbird for anything else.

So, for example:

Download and install the Thunderbird client
Set up imap email connection to a user on your server. Save PW in the PW manager (Sieve needs it to connect)
Menu (top-right), go to Addons & Themes, and install the Sieve addon
Menu->Tools->Sieve Message Filters (a separate menu choice from Tools->Message Filters)
NOTE: One (primary) script is “Active”, while many others can be Included from the Primary script. Sieve can edit any/all, either raw or with a smart editor

SYSTEM INFORMATION

Operating system Debian Linux 10
Webmin version 1.981
Usermin version 1.823
Virtualmin version 6.17-3
Authentic theme version 19.83-2

system · February 5, 2022, 10:22pm

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