We have just recently installed Zimbra as our mail server and we are experiencing some issues. We are able to send emails out, but when certain people try to reply to our emails or just even send a new email they get this error message. I was wondering if someone could help me out in resolving this issue. Thank you in advance.
Reporting-MTA: dns; powersmtp2.powereng.com
Arrival-Date: Tue, 9 Feb 2010 11:52:25 -0700 (MST)
Final-Recipient: RFC822; firstname.lastname@example.org
Remote-MTA: DNS; mail.domain.com
Last-Attempt-Date: Tue, 9 Feb 2010 16:06:16 -0700 (MST)
Will-Retry-Until: Sun, 14 Feb 2010 11:52:25 -0700 (MST)