[Dovecot] dovecot and outlook express and large messages

Hi

I have been using Dovecot 0.99.11 and 1.0-test52 on a server with about 2000 accounts. All has been working good until a few days ago. Now I'm stuck and can't work out whats going on.

The problem seems to be only with Outlook/outlook express clients. If the mail is large with an attachment its fails. After you hit the send and receive button after a while Outlook express gives the error "Your POP3 server has not responded in 60 seconds". Network activity seem to be minimal between the client and the server. There is no log entry out of the ordinary to say what went wrong. I have tried out a number of changes to the dovecot.conf file, none make any difference.

Thanks for any help.

Regards Daniel Rowe