Message audit log shows "Action taken: Rejected message by MTA"

Products

• Messaging Gateway

Issue/Introduction

When using the "Connection IP" filter, Message audit logs on Messaging Gateway (SMG) may display "Action taken: Rejected message by MTA" despite the "Verdict" field showing "None."

Symptoms

• The Message audit log shows "Action taken: Rejected message by MTA"
• The Verdict field in the log is "None"
• No associated reputation policy verdict is present.

Example

ID: 0ac85950-b7c36ae000004379-06-4ecdd99402c8
Message-ID:
Accepted From: 192.0.2.83
Scanners: Local Host
Time accepted: Thursday, Nov 24, 2019 02:43:48 PM JST
Direction:
Sender: (none)
Authenticated username: (none)
Original recipients:
Original Subject: (none)
Full attachment list: None
Suspect attachments: None
#  Recipient Data
Intended recipient: None
Verdict: None
Tracker: None
Actions taken: Rejected message by MTA
Delivery: None
Untested verdicts: None

Environment

• Product: Messaging Gateway
• Version: All versions

Cause

This behavior is by design. MTA DNS validation checks operate outside the scope of the Brightmail Engine and do not generate an associated verdict. This indicates that one or more MTA DNS validation checks are triggered and failing.

Resolution

1. Review MTA DNS validation settings in the SMG Control Center under Protocols > Settings.
2. Refer to the Messaging Gateway Administration Guide for detailed information on configuring these checks.