Messages not delivered due to reverse DNS mismatch


Article ID: 157354


Updated On:


Messaging Gateway


Reverse DNS checks fail, causing sent messages to not be delivered through Symantec Messaging Gateway (SMG). You may also see errors referring to a reverse DNS mismatch.


This issue is caused by mismatching DNS records or hostname on Messaging Gateway. When a DNS reverse (PTR) record returns a different name than the forward (A) record returns, or which appears in the Messaging Gateway SMTP banner's hostname.

Example of records that could cause this issue:

  • MX lookup for returns
  • Forward DNS (A) lookup for returns The reverse DNS (PTR) lookup for returns name
  • SMTP Header/banner reports "220 ESMTP Symantec Messaging Gateway"


  • Verify that the SMTP banner hostname matches that of the MX, A, and PTR record.
  • Check if Messaging Gateway is set to accept messages for multiple domains. In this case there may be several DNS MX and A records configured that direct mail to the Messaging Gateway for the domains, causing DNS mismatch errors or delivery issues.
  • Direct each of the domains to common MX records for a single hostname and PTR address, which will resolve DNS mismatches.


  • Messaging Gateway accepting messages for:,,
  • MX lookup for returns
  • MX lookup for returns
  • MX lookup for returns
  • IP (A) lookup for returns and the reverse (PTR) lookup for returns
  • SMTP banner returns "220 ESMTP Messaging Gateway"

To change the name reported in the SMTP greeting banner

  1. In the SMG Control Center, navigate to Administration > Configuration.
  2. Select the scanner being changed, and click SMTP > Advanced Settings.
  3. Change the "MTA host name:" field. and then click Continue.
  4. Click Save.