On Thu, Mar 13, 2008 at 3:36 AM, Timo Sirainen tss@iki.fi wrote:
Enabling rawlog (http://wiki.dovecot.org/Debugging/Rawlog) and looking at what exactly gets sent at that time could be useful.
I did it but I could't find anything useful.
Then I decided to use wireshark on the client PC and here is what I found: Mail clients are creating new connections to save sent mail to "Sent" imap folder. At the end of the authentication process the following helpful message is sent to client: "NO Maximum number of connections from user+IP exceeded"
Great. That's why. Our imap server is in dmz and all internal users are reaching this server natted from the same ip.
The fact is that error message doesn't appear in dovecot logs, and email clients don't say anything useful, either. (maybe dovecot should write it to /var/log/dovecot.log)
Increasing mail_max_userip_connections value should fix it.
Thank you all for helping me in solving this issue.
Regards, Diego.