We got complains from clients mails are not delivering to recipient. After reviewing mail queue manager from WHM. We found all mails were stuck in queue. We tried to deliver mail forcefully but got some error message.

R=dkim_lookuphost defer (-1): host lookup did not complete

After investigation the error message we found issue with DNS IP. After changing DNS IP it started working.

How to change DNS IP.

  1. You can change DNS IP from WHM if you have root access of server. Login to WHM

Click on Networking Setup » Resolver Configuration >>  proceed and  update IP

2. If you don’t have WHM installed on server so you can edit resolv.conf file.

nano /etc/resolv.conf


Hope this article will help you to resolve this issue.