What does the log message "verified no" mean?

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Updated:August 15, 2014
Document ID:118173

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Introduction

This document describes the meaning of "verified no" on incoming SMTP connections.

Background Information

Here is an example of a "verified no" log message:

Wed Nov 17 10:00:20 2004 Info: New SMTP ICID 353419258 interface
PublicNet(10.111.123.234) address 103.102.100.99 reverse dns 
host unknown verified no

Log messages of this type indicate the following:

  1. The IP address does not reverse resolve to a fully qualified domain name (FQDN).
  2. The hostname found from the Reverse Resolution does not Forward Resolve to the same IP address as is connecting.

This condition is often seen for ISPs with poorly maintained DNS records.

This condition will typically not cause mail delivery to fail. 

Cisco customers can throttle or block messages from domains with DNS issues.

Revision History

Revision Publish Date Comments
1.0
15-Aug-2014
Initial Release
TAC Authored

Contributed by Cisco Engineers

  • Stephan Fiebrandt and Tomki Camp
    Cisco TAC Engineers.

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