[Dovecot] Outlook 2010 very slow when using IMAP - are there any tweaks?

Charles Marcus CMarcus at Media-Brokers.com
Tue Jul 3 13:37:30 EEST 2012

On 2012-07-03 3:12 AM, Kaya Saman <kayasaman at gmail.com> wrote:
> However this is a clean server with plenty of space left on the pool
> allocated for mail and it's additionally using ZFS too.

What OS? ZFS implementation/version? How is mail stored (maildir? mbox?)

While I don't think this is your problem, just fyi, my understanding is 
that it is fairly easy to implement ZFS wrong (which would cause serious 
performance problems), and that the only decent ZFS implementation is 
Suns (ie, what ships with Nexenta), or the latest FreeBSDs...

Also, my understanding is that ZFS isn't the snappiest of filesystems 
even when properly configured (you trade performance for data integrity).

Personally, I'd recommend trying this on a traditional FS (XFS or 
Reiserfs for maildir) and see if that changes things.

On 2012-07-03 3:12 AM, Kaya Saman <kayasaman at gmail.com> wrote:
 > The point is that I am monitoring using nload as well as other things
 > and the maximum bandwidth being got with Outlook is a few Mbps burst,
 > average 50kbps; while with T-Bird I get way over 130Mbps?

Congrats - there's your problem... now you need to find out *why* this 
is so slow... most likely a tcp dump analysis of a session is the only 
way - I think there are people here who could help you analyze one (but 
not me, sorry)...

On 2012-07-03 3:41 AM, Kaya Saman <kayasaman at gmail.com> wrote:
 > The PST's seem to be stored on local hard disk too.

'Seem' to be? You need to make sure, because if they aren't that could 
definitely cause, or at least contribute to this kind of problem.


Best regards,


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