[Dovecot] Timed Out or Disconnect Errors on emails with attachments

[Tudor Holton]

Hello all,

I've migrated our Maildir system from Courier-IMAP-SSL to Dovecot with 
SSL and now we're getting "Connection to <server> Timed Out" errors when 
sending mail with attachments.  The mail gets sent, however it doesn't 
save the mail in the user's "Sent" folder. 

Our IMAP and SMTP servers are different.  So the client sends to the 
SMTP server first, completes that, and then opens a channel to Dovecot 
and dovecot appears to receive the data (TB gives a progress bar as it's 
sending to dovecot) and then disconnects _after_.

We have a mixed bag of clients here from Thunderbird on Linux and 
Windows, through Outlook Express to Outlook.  All show similar errors.

I enabled the logs on dovecot, however it wasn't very informative.  At 
the time it occurred the only line in the log file was:
dovecot: 2007-03-13 16:21:12 Info: IMAP(tudor): Disconnected

This is obviously different from "Disconnected: Logged out".

Emails without attachments behave ok, it only occurs with emails with 
attachments.

Has anyone else had any experience of this?

Cheers,
Tudor.