Zimbra is sending mail outside my network to itself and causing my system to exceed DynDNS's limits for sending mail / per day. I do not know what is generating this mail and it is stopping our users from sending mail - until I manually dump deferred mail que.
I have tried deleting the deferred mail que and it only fills back up again and the same cycle happens. DynDNS limits are hit and all mail stops flowing. SEE EXAMPLE BELOW
Does any one have a suggestion on how to stop this from happening?
Mar 6 09:19:00 mail1 postfix/qmgr: 9DC4F257702: from=<email@example.com>, size=1696, nrcpt=1 (queue active)
Mar 6 09:19:01 mail1 postfix/smtp: 9DC4F257702: to=<firstname.lastname@example.org>, relay=outbound.mailhop.org[18.104.22.168]:2525, delay=538, delays=537/0.05/0.65/0.04, dsn=4.0.0, status=deferred (host outbound.mailhop.org[22.214.171.124] said: 451 Daily Message Quota Exceeded (in reply to MAIL FROM command)