For several years, I've been saying Apple made a bad choice when they picked Cyrus IMAPd as the POP/IMAP server for Mac OS X Server. It's a huge and complicated system, encompassing IMAP, POP, SSL, Sieve filtering, LMTP delivery, USENET news, clustering/proxy (Murder), pluggable authentication (SASL), etc. I cannot think of a single company outside Cupertino where it would make sense to run an enterprise mail system on Mac OS X Server, but Apple continues to add these inexplicable high-end features to its mail server, most recently XSan-based email clustering in Leopard Server.
The statement that convinced me (shortly after I had migrated to Cyrus IMAPd on Mac OS X Server 10.4 "Tiger") that I would never choose to run Cyrus for my personal use, was the following -- which I came across again today:
This system should be expected to have the same order-of-magnitude installation complexity as a netnews system. Maintenance should have similar complexity, except administrators will have to deal with creation and deletion of users and will have the option of managing quotas and access control lists.
USENET news is infamously demanding and bandwidth intensive. It would be wonderful if Apple had taken Cyrus IMAPd, repackaged it (without too many changes!), and put a powerful and simple interface on top. The did this quite successfully with Apache httpd (although Server Admin breaks down on complicated configurations and has obscure bugs). Lots of people use Mac OS X Server to run websites and think it's easy & simple. Considering the typical reactions of those same people to the
.conf files "under the hood", this is a noteworthy triumph. Similarly, Time Machine provides a reasonable approximation of scheduled snapshots on a high-end NAS for do-it-yourself file recovery, with a simple interface that insulates users from the nitty-gritty of copy-on-write and hard links.
Cyrus did not get as much attention, though. Basically, Apple makes it pretty easy to create email accounts, provides a Repair button for the overall Cyrus database, and provides a Reconstruct button for individual accounts. That's about it. Unfortunately, Apple doesn't really document maintenance beyond "press the button and it will fix your problem". I've had several serious database problems which Apple's Repair button did not help with. Those were bad times.
Similarly, I have had problems where users could not log in, but Workgroup Manager claimed their accounts were usable. I eventually discovered that resetting passwords with
passwd works sometimes, and re-setting passwords in Workgroup Manager works consistently, but when I asked Apple about it, the eventual response was basically, "Yes, that's bad; you should restore your accounts from your recent Open Directory export." Not a good answer.
It doesn't help that Apple's SpamAssassin and ClamAV installations are broken, as these result in more spam and slower deliveries.
So why am I planning to migrate to Cyrus IMAPd on CentOS 5.1? Well, I'd really like to just copy my 5gb mail directory to the new system and have my clients not notice the difference. Eudora doesn't handle (IMAP) change well -- renaming a single IMAP directory can force it to download all messages again, and various other things can cause Eudora to lose date stamps on sent mail, or message state information (when it gets disassociated from the actual message on the IMAP server). If I can make Cyrus work, I'll be very happy, and if I can't I'll try Dovecot (Red Hat's default) or Courier (which I hear is also good).
Also, I know it can work, and I have a rough model to work from on my Tiger Server, but if I wasn't using Cyrus already I would stay away from it, as I wish Apple had done.