Delivery to the following recipient failed permanently, Verification failed

Today, I was getting the following error while trying to send email to any account of the server. The mail bounced with the following error messages.

This is an automatically generated Delivery Status Notification

Delivery to the following recipient failed permanently:

[email protected]

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550-Verification failed for <[email protected]>
550-The mail server could not deliver mail to [email protected]  The account or domain may not exist, they may be blacklisted, or missing the proper dns entries.
550 Sender verify failed (state 14).

I have found a lots of comments internet regarding this. As, it was a cPanel server, I searched their forum too. Whatever I was getting was not solution for this problem.

Later, I have found that the resolver for the server is not working. I tried to get A record of google.com from that server, it says:

google.com has no A record

Similarly, ping also failed.

Then I have opened the /etc/resolve.conf file and put the following line at top and everything then started working like magic:

nameserver 4.2.2.1

Got same problem? Try this before hair pulling. It applies to non-cPanel server too.