SMTP Code: "450 4.7.1: Helo command rejected: Host not found"

Products

• Messaging Gateway

Issue/Introduction

Messaging Gateway (SMG) fails to deliver messages to a specific destination domain and messages are queued in the Delivery queue with the following queue status:

450 4.7.1 Helo command rejected: Host not found

Cause

The hostname used in the SMTP greeting issued by Messaging Gateway as part of the HELO or EHLO command does not resolve to an IP address in the DNS and the destination mail server is rejecting delivery due to that failure.

Resolution

The hostname value configured in Administration > Configuration > host > SMTP > Advanced Settings > Delivery > MTA host name needs to be configured in the DNS with an A record that resolves to the public facing IP address used by Messaging Gateway.