We have a Zimbra mail server and we are facing some issues from other MTAs trying to verify recipients.
The other MTA (spam filtering, etc.) is getting the following error:
Milter: from=<address@domain.com> reject=451 4.3.2 Please try again later
We are checking milter.log but we don't get any conection from the other MTA. Besides, milter filters are only for distribution lists and the addresses showing out in the errors are user names, not distributions lists.
It is also quite strange that the system is working after a kind of reset but after a while we are getting back the errors.
Any idea of what could be?
