We recently got an undeliverable message in response to an email a user tried to send. It says:
Your message was rejected by this user and was not delivered. Reason: Messages from your location are rejected, identification (HELO) has no matching DNS entry. Protection provided by: MagicMail version 3.0 For more information, please visit the URL: http://www.linuxmagic.com/best_practices/resolve_helo_domain.html or contact your ISP or mail server operator. 1bb22856-ac5e-11e8-a57d-005056bbe21e
All other mail seems to be flowing fine, and this is the only rejection we've received. From what I have researched and found so far, it looks like the cause of the issue is that the Exchange (2010) server is showing an incorrect SMTP banner of servername.domain.local. And when I look in the EMC under Organization Configuration > Hub Transport > Send Connectors > External Mail Connector, the "Specify the FQDN this connector will provide in response to HELO OR EHLO" field is empty. I assume I just need to enter our public SMTP server address here.
This is my guess as to how to fix this problem, but since I'm not sure I'm hesitant to make this change. Can anyone verify, or point me in a new direction if this is not accurate?