[Kenny]

One of the clients had issue receiving email
Error was

<support@***EDITED***>:
64.235.53.54 does not like recipient.
Remote host said: 550-(emailserver2.asdf456.com) [72.18.207.139] is currently not permitted to
550-relay through this server. Perhaps you have not logged into the pop/imap
550-server in the last 30 minutes or do not have SMTP Authentication turned on
550 in your email client.
Giving up on ***EDITED***

Positing the solution in forum for other clients and general Internet users

Login via ssh and enter

#grep domain.com /etc/localdomains

replace domain.com with your domain name.
If entry is missing, then place it in /etc/localdomains using nano or emacs.
It should resolve the issue.