GEEK: Thunderbird IMAP slow

[archerships]

I’m using Thunderbird (version 2.0.0.0) on a 2.16 GHz Intel Core 2 Duo (1 GB Ram) running Mac OS X 10.4.9. When I connect to my account at fastmail.fm via IMAP, it frequently takes several minutes for each folder to open, and when I send mail, it often takes several minutes to copy the sent mail to the Sent folder (and sometimes it fails altogether.) Has anyone else experienced this problem? Any suggestions for what I might do to debug it?

[Edit: This has been going on for a couple of weeks, and happened when I was running the previous release of Thunderbird. If I stop and restart Thunderbird, it goes away for a while. ]

Thanks!

Original: craschworks - comments

Comments

[madbard.livejournal.com]

I use Thunderbird 1.5 for IMAP mail. Though the delays are longer than the snappy POP3 response, they're not as severe as what you're describing. It may well be an issue with the speed of your mail server.

[crasch.livejournal.com]

Yeah, it may be the servers. Although it happens with both my work server and fastmail.fm. It seems unlikely that both would be sluggish at the same time.

[madbard.livejournal.com]

I may be wrong about this, but I think the CPU load on the client side is trivial. Thunderbird tells a server to move message XYZ to folder ABC, then waits until it gets an acknowledgement before reflecting this change in the user interface. If you click on the "go offline" button, you'll see that response time for these operations is near-instantaneous. So the latency is very likely the fault of your server(s) or the intervening connections.

[crasch.livejournal.com]

Thanks! I think you're right about how IMAP works. Perhaps both servers I connect to are simply overloaded, or there's a problem with my network connection.

[h-postmortemus.livejournal.com]

So how big sre the folders on the server?
IMAP is a more complex protocol than POP3, with a lot of extra features. But because POP3 is so wildly popular, a lot of implementations of IMAP servers are not optimized. Or the vendor has not configured an optimal scheme for IMAP folder storage.

I'm going to guess that you have relatively large folders on the mailserver (i.e. 500k+, or many megabytes). If these are stored as single files on the server than the delay would be due to seeking to the end of the file. Which should only take seconds, but poor tuning of filesystems or bad IMAP implementations may make it take much longer.
A better IMAP folder storage method uses an actual directory for each IMAP folder and messages are stored individually. This requires more individual files and is less space efficient, but obviously can give better returns on performance.

Alternatively, the providers are just slow. Or, you have some application running on the Mac that's transparently proxying the IMAP connectivity and doing something to it (i.e. an e-mail security program). I had problems with IMAP for a while until I discovered my PGP Desktop software was proxying the connections. Unfortunately, PGP Desktop assumes I'm using Outlook or some other mainstream e-mail reader and I use PC-Pine.

HTH. HAND.