554 5.4.6 Hop count exceeded - possible mail loop

Products

• Messaging Gateway Hardware

Issue/Introduction

Messages for a specific domain or email address are not being delivered as expected. Reviewing the Message Audit Logs for one or more failed messages shows the following SMTP error code:

554 5.4.6 Hop count exceeded - possible mail loop

Cause

This SMTP response indicates that there is a mail loop in the environment. Messaging Gateway is routing abd deliverying the domain or email address as configured but the message is then being routed and delivered back to Messaging Gateway. As the message traverses this routing loop, it accumulates Received headers until one of the email servers in the loop detects the mail loop and refuses delivery with an SMTP code that causes the undeliverable message to be deleted.

Resolution

1. Review the Messaging Gateway Protocols > Domains page to ensure that the email route for the affected domain or email address is correct and points to a server that will both accept the message and properly route it to its final destination.
2. If SMG is routing the messages to an internal email or Exchange server, check the destination server configuration to ensure that it is configured to accept the domain as local or routes it to another mail server rather than back to Messaging Gateway