DigitalOcean + ServerPilot + SMTP - EMails not sending

[Case]

I've got xenForo running on a DigitalOcean which I setup through ServerPilot. I have the front end files on one droplet and a separate droplet for the remote database.

All seems fine apart from emails not being sent.

I'm guessing its an issue with the database being on a separate server.

I've checked that postfix is installed.

The error I'm getting in postfix is:

May 30 10:41:25 tfc-web postfix/smtp[9579]: 71C73A4A52: to=<email@domain.com>, relay=none, delay=0.06, delays=0.03/0.03/0/0, dsn=4.4.3, status=deferred (Host or domain name not found. Name service error for name=domain.com ty$

Thanks

 

[Paul B]

See point 1 of the guide here for typical causes of that error: https://xenforo.com/community/resources/email-troubleshooting-guide.5086/update?update=18730