Linux Mail Delivery Failed With DNS Service Unavailable Error and Solution

Q. I get following error message for my postfix email server:

Mail Delivery Failed With DNS Service Unavailable Error and Solution

How do I fix this problem?

A. You need to setup full qualified domain name (FQDN) using dns server to avoid this error message. The remote mail server receiving the mail from the local server is unable to resolve the local mail server's hostname. For example, if you set local mail server name to lansmpt.example.com, make sure it can be queried using DNS and have a valid working fully qualified domain name.

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