SYMPTOMS

Error (MTA-1010): Message (MessageID) could not be delivered as an infinite message loop was detected.

CAUSE

Message looping is often associated with store and forward mail servers. For example, if MailEnable is configured to smarthost all mail to itself, then mail would (if left undetected) cycle within the mail server infinitely.

e.g.  MailClient->SMTP (Inbound)->MTA->SMTP(Outbound)->SMTP(Inbound)->MTA->SMTP (Outbound) and so on.

Other possibilities exist (particularly with list servers and groups). Suppose a message is sent to a distribution list and the list had an invalid address. The reply from the list would be sent to all users, and the message to the invalid recipient would bounce. This bounce could be sent to the list and then distributed, where it would bounce and so on.

e.g.  SMTP (Inbound)->MTA->LISTSVR->SMTP(Outbound)->SMTP(RemoteBounce)->SMTP(Inbound)-> and so on.

Hence MailEnable's MTA implements message loop detection that keeps track of messages as they pass through it. If a message passes through the MTA too many times, then MailEnable detects that the message is in an infinite message loop and places the message in the Bad Mail Folder.

RESOLUTION

In most cases this is caused by configuring MailEnable to smart host back to itself. Hence, ensure that the SMTP connector is not configured to smart host to the MailEnable server or, that a domain has been smarthosted back to the MailEnable server.

Use the message tracking utility  from the MailEnable download page to analyse where messages are being moved within MailEnable. The SMTP and Debug logs should also assist in determining why message looping is occurring.

MORE INFORMATION

How to troubleshoot mail looping issues: http://www.mailenable.com/kb/content/article.asp?ID=ME020269

How do messages end up in the BadMail Directory?: http://www.mailenable.com/kb/content/article.asp?ID=ME020169