[Dovecot] Duplicate message with POP3 and Outlook

[Michael David Joy]

I can say pretty confidently that it's something specific about your
configuration, and not specifically outlook/dovecot.

I've run Dovecot .99.10->.99.14 on a Debian box for the past few years
and running pop with mail saved on the server, or not saved, with
Outlook 2000-2003, Evolution (many many different versions 1.x-2.x),
Outlook Express, Netscape Mail, Mozilla Mail etc... and I've only seen
this behavior when having connection troubles. Also, this is with many
different version clients accessing the same account (ie work/home
linux/windows mac/windows linux/mac etc...).

My best guess would be that the client is getting disconnected from the
server mid-email download and the messages aren't getting deleted. If
memory serves correctly, Outlook doesn't do cleanup until after all the
messages are downloaded? Or at least a few versions do this.

One other idea is that perhaps some large attachments are causing disk
IO to choke or otherwise slow down and the client is reconnecting and
downloading the message again once it's been cached? I've seen our mail
server choke a few times with multi-megabyte attachments and do this,
but it was because the IDE disk with mail was running in PIO mode (dma
disabled due to bad sector detection). We've since moved to sata raid
systems for more redundancy.

Are you running SSL or anything other non-stock authentication/mailstore
configurations that aren't exactly 'stock'?

Michael Joy
HEP - University of Mississippi
mdjoy at phy.olemiss.edu

On Wed, 2005-02-16 at 05:35 +0100, St0rM wrote:
> I know that what I am about to say is FOR SURE a problem of Outlook and 
> Outlook Express, but since I can't find any know bug like this, and all 
> is started when i switched to Dovecot (and I can't exclude is somehow 
> related to Dovecot), I would try to ask for help here, maybe someone of 
> you already seen that.
> 
> I am using dovecot 0.99.13 on a Fedora 1 (0.99.13-1).
> 
> The problem I see is that, when a customer using Outlook or Outlook 
> Express (many different versions, from Outlook 2003 to Outlook Express 
> 5, with various patch) via POP, every mail is downloaded TWO times, more 
> precisely the first time on the first connection and the second on the 
> second, where the mail gets finally deleted.
> 
> I tried manually and with many other clients, and pop actually works 
> perfectly, and IMAP too. Outlook client have NOT the "Leave mail on 
> server" option checked, and nothing similar is around.
> 
> I am about to start a sniffing session but it would be problematic for 
> privacy questions, and I'm not able to reproduce it so easily, as it 
> seems only some of our customers with Outlook have this problem, and the 
> (few) trial I've done here seems to go smoothly. So I fear it will be a 
> LONG week.
> 
> Again, i bet it's an Outlook problem, but... Anyone already seen 
> something similar?
> 
> Thanks for the help, and for the time. Keep up the good job.