Troubleshooting mail looping issues.
One indication of abuse or mail looping is a dramatic increase in the size of the SMTP log files. If this occurs, check the server to determine whether it is running as an open relay (hence spammers are probably using the server to send out spam - giving the impression that the server is looping).
Review this at: http://www.mailenable.com/tools/memaillookup.asp
(The local Diagnostic Report will also have warned about this issue).
Although this may be the cause, review the log files to determine the source of the loop (whether its coming from the server or otherwise). The logs will indicate where the mail is coming from and going to.
The only situations where looping can occur are:
1 - The SMTP connector is smart hosted to itself (Diagnostic Report will warn)
2 - A domain is smart hosted to itself (Diagnostic Report will warn)
3 - A mailbox is redirected to another mailbox that is redirected to itself (the MTA Debug log should contain an error indicating that looping has occurred).
4 - Quotas have been specified for Catch-all or Postmaster mailboxes (this is undesirable)
To diagnose looping issues, review the MTA log and determine which message(s) are looping. Relate these to the SMTP connector and determine the source of the loop.
Open Relay abuse can be identified by reviewing the SMTP log files where you should see a huge amount of mail destined to yahoo, hotmail and aol accounts.
(MTA-1010): Mail Transfer Agent - Infinite Message Loop Detection:Article ME020076
How to direct SMTP Outbound mail to another SMTP host:Article ME020157
|Product:||MailEnable (All Versions)|
|Keywords:||looping SMTP MTA|
|Class:||TRB: Troubleshooting (Configuration or Environment)|
|Revised:||Wednesday, May 4, 2016|