Another post for the peripheral brain.
When I first set up my own server lo these years ago, I never really thought about email message filtering. After all, I had rules in Mail.app that would send my incoming message to wherever I wanted them. Besides, I was much more concerned with eliminating spam.
Well, that was then and spam seems under control. I was prompted to look at server-side message filtering mostly to help out my mother, who seems determined to have every single store, travel and other consumer site that will happily take your email address and send you messages daily — or more often, have a more controllable experience on her iPhone. When we originally set up her iPhone she told me she didn’t want to use it for email. Silly me, I listened and set her up with a POP account. Well now she wants email. What’s a good son to do. 😉
I changed her POP account to IMAP, copied over all her messages to her new IMAP folders and thought I’d need to solve her impending problem of 100 or so messages every other day choking her inbox.
After a bit of Googling I found Sieve. I’d actually heard of it before but never really thought about it. The Apple Discussion Forum had a nice start and pointed me on to sources I used to set it up.
Here are the salient points. From the terminal…

1. Add the following lines to /etc/services

   sudo pico /etc/services
   

   Insert the following lines.

   callbook 2000/udp # callbook
   callbook 2000/tcp # callbook
   + sieve 2000/udp # sieve mail filtering
   + sieve 2000/tcp # sieve mail filtering
   

   You can check to see if it’s running by running

   netstat -an | grep 2000
   

   with results

   tcp4 0 0 *.2000 *.* LISTEN
   tcp6 0 0 *.2000 *.* LISTEN
   

2. Create /usr/sieve

   sudo mkdir /usr/sieve
   sudo chown _cyrus:mail /usr/sieve
   

3. Restart mail services

   sudo serveradmin stop mail
   [ some stuff ]
   sudo serveradmin start mail
   [ some stuff ]
   

4. Since I’m using OS X Server and SquirrelMail is already running, next was installing and configuring avelsieve.

I really did try installing the latest development version — 1.9.9 alpha. That should have been a clue. After spending way too much time with it I installed the stable version – avelsieve 1.0.1. Once copied into /usr/share/squirrelmail/plugins run sudo perl /etc/squirrelmail/config/conf.pl and activate the plugin.
Then it’s back to the terminal. These instructions are from AFP548.

    cd /usr/share/squirrelmail/plugins/avelsieve
    sudo cp config-sample.php config.php

Now set the correct authentication matching SquirrelMail.
Edit /etc/squirrelmail/plugins/avelsieve/config.php and change:

$preferred_mech = "PLAIN";

to

$preferred_mech = "CRAM-MD5";

You should be running SquirrelMail with CRAM-MD5 authentication anyway.
Finally, edit the /etc/squirrelmail/plugins/avelsieve/lib/sieve-php.lib.php file.
Find the line:

fputs($this->fp, "PUTSCRIPT "$scriptname" {$len+}rn");

and change it to :

fputs($this->fp, "PUTSCRIPT "$scriptname"".' {'."$len+".'}'."rn");

This fixes an error in the script allowing you to save your changes to the filters. Now go login to webmail and click on the Filter link to start creating your Sieve filters.