dovecot & Apple Mail & maildir & lots of Mail

[Thomas Klausner]

On Fri, Nov 21, 2014 at 10:52:38PM +0100, Thomas Klausner wrote:
> I have dovecot 2.1.12 running on a mail server, and recently
> configured Apple Mail to connect to it using secure IMAP, for the
> first time.
> 
> At the beginning it just showed the inbox and everything was fine, but
> then I wanted to look at some of my folders and found the 'subscribe'
> menu. When I opened it, Apple Mail went to discover what mailboxes
> there are, and that's where my trouble began.
> 
> It seemed to make good progress for some time (though slow -- over
> days), and now lists the mailboxes from starting with letters a to d
> on the left hand side (filling all the visible space, so there might
> be more). However, whenever Apple Mail gets focus, the cursor becomes
> a spinning rainbow circle and I can't interact with it.
> 
> I tried deleting the mail account and setting it up again. The inbox
> was shown again immediately and Apple Mail was usable, but the first
> time the cursor moved over the mailboxes on the left hand side, it
> froze again.
> 
> There were two imap processes on the server, one rather idle, the
> other eating CPU for about two minutes, then idling, and some time
> later it disappeared too.
> 
> My Mail directory is 31G with about 180 directories, each containing
> mails in maildir format.

One thing that happened twice now is that files like these appear:
/home/user/Mail/dir/cur/.imap/1312388125.11233_28123.host:2,S/dovecot.index.log
but they don't go away for days.

How can that happen?
Can/should I delete these files?
 Thomas