[Dovecot] Outlook 2007 & 2010 hangs in v2.2?

Andy Dills andy at xecu.net
Fri Jun 6 14:25:08 UTC 2014

We just upgraded from 2.1.16 to 2.2.13, and we have been have horrendous troubles with outlook since the upgrade.

For users with large mailboxes, they are unable to sync their folders. Perhaps this is specifically because of the problem you are mentioning Timo.

The only solution we could come up with for now was to configure outlook to only fetch headers and not bodies, when syncing. For the most part, bringing up individual messages is fine, haven't seen that fail. So, with that tweak to the outlook config, things are working error-free again for our users...but it was certainly an unexpected situation to tackle.

Also, we found a marked improvement connecting via SSL on 993 than we do unencrypted on 143.

I can definitely confirm 100% there is a regression in dovecot 2.2 that severely impacts the performance of outlook (but works great with everything else).

Let me know if I can help you track this down Timo.


Sent from my iPhone

> On Jun 5, 2014, at 1:40 PM, Timo Sirainen <tss at iki.fi> wrote:
>> On 5.6.2014, at 20.23, Robert Schetterer <rs at sys4.de> wrote:
>> Am 05.06.2014 17:02, schrieb Timo Sirainen:
>>> On 5.6.2014, at 17.41, Martin Rabl <martin.rabl at rablnet.de> wrote:
>>>> Am 05.06.2014 16:38, schrieb Timo Sirainen:
>>>>> Has anybody noticed Outlook 2007 & 2010 (but apparently not 2013) hanging IMAP connections with Dovecot v2.2 (but not v2.1) when they're FETCHing large mails? I can't think of any reasonable explanation for this.
>>>> how large?
>>> I don't know yet if the mail size is even relevant. At least one hang was caused by downloading ~55 MB mail where it stopped just before the last 400 kB.
>>> I find it strange that v2.2 has been out for a long time and nobody before this complained about any hangs.
>> 55 MB mail may are rare ,i can test it ,but it will need some time ( old
>> outlook install on clean new windows system....)
>> perhaps anyone has an existing setup which could do it faster
> Happens also with smaller mails, for example 3 MB and I think there were also even smaller ones like 1 MB. I see that once Outlook tried to download the same 3 MB mail 3 times and it stopped reading it when it had 400 kB left, but the 4th time succeeded. Dovecot sent exactly the same data with the same TCP packet boundaries all times (at least to Dovecot proxy - would have to look with tcpdump further to see if proxy does something differently..)
> Anyway, nobody in general has had trouble with Dovecot v2.2 and Outlook 2007/2010? Maybe the problem is something else, although strange if it started happening only immediately after Dovecot upgrade.

More information about the dovecot mailing list