About a year ago (2008) we were getting NDRs because our reverse DNS (RDNS) PTR was not set correctly but we fixed that. Recently our users started getting NDRs of various types again but it is not the reverse pointer this time.
Quick:
Fix FQDN on the SMTP Virtual Server.
Visual:
Learning:
We starting getting a number of different NDR errors and I assume this is because of companies tightening up on thier SPAM filtering.
Errors included:
The following recipient(s) could not be reached:
FOLLOWED BY EMAIL ADDRESS THAT IT FAILED TO SEND TO AND ONE OF THE FOLLOWING REASONS:
You do not have permission to send to this recipient. For assistance, contact your system administrator.
FOLLOWED BY DIFFERENT MESSAGES LIKE:
-Helo command rejected: Host not found
-Client host rejected: cannot find your reverse hostname
-Requested action not taken: message refused
-ETC.
We send email out as:
userName at OurExternalDnsName.com
Our mail server connects as:
InternalDomainName.com
The thought was that perhaps the receiving servers were trying to validate the Internal Domain Name and failing. I changed the name that the SMTP Virtual server connects with and that solved the problem.
See visual above:
In Exchange System Manager
Select the Default SMTP Virtual Server and right click for properties
Select the Delivery Tab and the Advanced button
Change the Fully Qualified Domain Name to the External DNS name for your mail server.
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