"Sender aborted connection" followed by "Message rejected by MTA" for some senders

Products

• Messaging Gateway

Issue/Introduction

You have found specific sender messages are not being delivered to the Messaging Gateway. A review of the Message Audit Logs shows that the sender has a pattern of one message transaction with the verdict "Sender aborted connection" immediately followed by a separate transaction with the verdict "Message rejected by MTA".

Cause

The sender may be performing suspicious SMTP transactions by sending a RSET command command after starting, but not completing, an SMTP transaction, then immediately starting a new SMTP transaction. If the sender's connected IP does not have a good Connection Class status, then the second SMTP transaction may be crossing the number of messages per transaction limit for the lower class.

Resolution

If the sender is a trusted sender, then adding the sender's IP to the Local Good Sender IPs list will bypass the connection class limit.

Additional Information

The Local Good Sender does not bypass all verdicts. More information on Local Good Senders is available here:

Functions bypassed in Messaging Gateway through domain or IP Good Sender lists