Reverse DNS does not match SMTP Banner

Products

• Email Security.cloud

Issue/Introduction

Some third party tools may display warning while doing domain health check: Reverse DNS does not match SMTP Banner

Environment

Email Security.cloud

Cause

The SMTP banner issued by clusterXa.YY.messagelabs.com email server did not contain the hostname resolved for server’s IP address.

Resolution

Email servers answer connections on port 25 with a string of text called an SMTP Banner. The purpose is to announce the server and any information that the administrator would like to convey to the world.

It is best practice to put the name of the server in the SMTP banner so that anybody who connects via IP Address has a clue as to who he is talking to.

This is not an error, but a warning that the presented name is not in the same domain as the hostname got from a PTR lookup on the IP Address.