[PLUG] Email server performance

[Aaron Burt]

On Fri, Apr 15, 2005 at 11:17:50PM -0700, Robert Anderson wrote:
> On 4/15/05, Aaron Burt <aaron at bavariati.org> wrote:
> > At my last job, we had a problem with performance using UW IMAPd and
> > mbox files.  What was happening was that several users would let their
> > inboxes get big (tens of megabytes). 
> 
> We've got users with mailboxes that are hundreds of megabytes.

Oog.

> > Then their mail client would
> > trigger a scan through the entire mbox file whenever it did a
> > mail-check, typically every 5 minutes.  This killed memory, disk,
> > network and CPU.
> 
> Do you recall what client, or does any imap client do this?

Mozilla mail, mostly.  But with UW-imapd, it could be any client; IIRC
it scans the whole dang file whenever you do a newmail.   Oh, and I
was wrong, it doesn't kill the network, just the other three.

You might take a look at this:
http://www.squirrelmail.org/wiki/en_US/FolderListWithUW
Like lots of docs, though, it advocates replacing mbox with maildir,
which may or may not give you the performance gain you're seeking
(depending on the filesystem) but would be disruptive to users.

Dovecot works with maildir or mbox format, and it keeps indexes so it
doesn't have to rescan big mail folders.  I'd recommend swapping it in
instead of UW-imapd.  (Try it on a testbed first, of course.)
http://dovecot.org/