Symantec Messaging Gateway (SMG) shows messages in the delivery queue with the message "421 4.4.0 [internal] no MXs for this domain could be reached at this time".
This is not an error but a description of why the message could not be delivered. The message indicates a general mail delivery attempt failure in which the appliance could not communicate with the remote mail system. This may be the result of an inability to successfully connect to the remote host, to resolve the MX records, or to resolve the DNS host names for the email domain to which the appliance is attempting message delivery. This can also be seen if a Control Center host's Quarantine SMTP listener is not available on port 41025.
Possible circumstances that may cause this issue:
The local MTA (SMG) cannot communicate with the remote MTA.
Connection refused by remote MTA
Connection times out while trying to connect to the remote MTA
Mail Exchange (MX) record(s) and A records missing
Firewall rule blocking connection from local MTA IP address
A remote Control Center's Quarantine SMTP listener is not available on port 41025 (for Quarantine bound Email)
The SMG setting that controls which IP interface is used for delivery of non-local messages can be found by connecting to the SMG's GUI and navigating to Administration -> Configuration -> <scanner> ->SMTP -> Advanced Settings -> Delivery.
If the command above fails, then the message returned will indicate whether the target IP address cannot be reached, times-out, or is rejecting the connection
If the command above succeeds, then the original failure may have been due to an intermittent connectivity issue
Imported Document ID: TECH93089
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