Resolving Email Queuing and Delays Caused by DNS Resolution Errors

Products

• Email Security.cloud

Issue/Introduction

Emails sent to the external recipient are delayed. The Track and Trace shows:

Response: 421 4.4.4 [internal] Domain Does Not Resolve

Environment

Email Security.cloud

Resolution

The issue is mostly related to the incorrect DNS configuration for the recipient's domain. The error '421 4.4.4 [internal] Domain Does Not Resolve' appears when the nameserver is unable to retrieve requested MX record, so the message delivery is delayed. Email is queued for the retry.

Use third party tools to verify if DNS lookups for the recipient's domain are successful. Contact Support in case of any questions.