For many years now (since before I started working at the University) we’ve been using University of Washington’s IMAP and POP daemons. They worked well, and (through an old bit of unsupported code) also allowed our MH users to access their email.
As time went on people wanted to do more than UW’s software could offer. Things like nested folders, and server-side caching. That’s when we started running Courier IMAP in parallel. This worked, but required users to use a non-standard set of port numbers.
At the time we looked at Dovecot, but it was fairly new, and we were unsure about trusting it with all our users’ email. That was a few years ago, so I decided this week to take another look. This was mainly driven by demand for faster IMAP access to the Maildir folders served by Courier IMAP.
My first impressions were good. I read through much of the stuff on the Dovecot wiki, and I kept thinking and saying to my colleagues “wow, that’s really neat”. Dovecot came across as a well thought out and well structured program, with a vast amount of useful tips and configuration ideas on their website. The level of customisation was good too, right down to allowing you to write a shell script to put in-line and tweak configuration to meet your exact needs.
After a few days of fiddling around I’ve managed to get a setup working that can replace both of our ageing Courier IMAP and UW IMAP installations. It should be a fairly seemless transition for our users, but I’m sure it won’t be that simple in practice. I’ve written a shell script that automatically detects at runtime where a user’s mail might be and sets the configuration accordingly. The script also allows the user to override the mail location and turn on debugging options.
And then there’s the performance issues. One of my colleagues has been having issues with the speed of Courier IMAP, and so far he’s impressed with Dovecot. The main gain here was the ability to store indexes in a separate location. Our mail is stored on an NFS server which becomes a performance bottleneck when using Maildir. Dovecot works around this by storing indexes and caches on a local disk making response times better.
Finally, there’s support. I hit a couple of issues getting things set up so I made use of the Dovecot mailing list. The response times in both cases were brilliant, and in both cases I got an answer to my problem straight away (maybe I asked common or stupid questions? 
).
So Dovecot comes highly recommended from me. Give it a try!
(And what about the MH users? Thankfully most have moved on to other things like Maildir & Thunderbird.)
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