Thursday, January 25, 2007

Thunderbird's "too many connections" message and Courier IMAP

When we use Mozilla Thunderbird at my workplace for our IMAP mail, Thunderbird often tells us that we have too many connections. It makes going through my folders impossible. This article explains that it's because Courier IMAP (which is used by Plesk) limits the number of connections from a single IP address to something like 4. Since we're all behind a firewall, we're all considered to be one user, as far as the server is concerned. I just had to change the values of MAXDAEMONS and MAXPERIP in /etc/courier-imap/imapd to allow more connections. Mozilla Thunderbird caches something like 5 connections by default, so even one user will put the IP past the limit.

While I was figuring my way around this problem, I set up another server to copy my mail over. It's an Ubuntu machine and I just used the distribution's Courier IMAP, but since I've been using UW-IMAP all these years, the configuration process for getting a system user up and running was completely foreign to me.

It turns out all I had to do was run this as that user in the user's home directory:

maildirmake -S Maildir

So now I have a nice little IMAP setup, pretty much out of the box. Some assembly required, apparently. To really understand it, I should do some deeper reading of my source for this command.

One problem with my setup right now with this single command is that it's not yet integrated into the MTA on the system, so that mail can't be delivered into that mailbox, only copied via IMAP in a mail client such as Thunderbird.