[Dovecot] Thunderbird very slow startup, 1.2.11, mbox, postfix local delivery to /var/mail

[Stan Hoeppner]

I've Google'd to exhaustion and can't seem to find an answer to my problem.
 I'm not sure if the problem is TBird 3 or my Dovecot setup.

The basic problem is that when I launch TBird and it grabs messages upon
startup, it takes forever to supposedly pull them down.  Once it's got them
they sort relatively quickly into the proper IMAP (dovecot) folders.  I
don't use sieve yet; I sort with TBird rules.  I don't sync messages for
offline use.  The only thing TB stores locally is the index cache, which I
deleted and had TB rebuild once, which didn't help.  All that did was waste
more time, as I've got 40,000 messages in my IMAP folders which had to be
re-indexed by TB.  (I save all list mail for future searching).

As an example of this problem, I'd not checked my email for just over day,
had ~300 messages waiting in /var/mail/stan.  TBird starts pulling them from
dovecot and says in the status bar "downloading x of ~300".  As I watch the
count tick up +10 at a whack, the TB process is pegged at 100%, there is
zero network activity, and the imap process on the server shows zero cpu
use.  It took over 60 seconds to "pull" the messages, after which TB sorted
them.  During the apparent sorting process, there is quite a bit of network
activity and the imap process on the server is relatively busy.  I say
"pull" in quotes because the entire time TB is saying it's pulling more
messages there is no network activity.  The client and server are plugged
into the same 100BaseT FDX switch (FDX verified), and the server has zero load.

I know TBird isn't the greatest IMAP client around, but I think taking over
60 seconds just to download ~300 messages is way too damn long given the
hardware resources, network, and load on the client and server machines.

TB basically seems to be pulling, or dovecot serving, only about 5
messages/sec over 100Mb ethernet, which is abysmal performance given neither
the server nor client have any load.  The messages are mostly list mail
which are at max a few kilobytes each.

I'm leaning toward a problem with TBird but I've been unable to find a bug
report that covers this, nor a forum post anywhere, etc.  The closest I've
found for "slow startup" are recommendations to compact folders.  I have no
local folders to compact.  I delete immediately and expunge on exit.

Anyone have any ideas?  Other than switching to LDA+sieve and have TB check
the IMAP folders for new mail?

-- 
Stan