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.