cPanel/WHM: Fix for 550 Access denied - Invalid HELO name

[Big Dan]

I have a CentOS VPS server running WHM/cPanel. Lately, I haven't been receiving email notifications from my forum hosted on this server. Long story short, I looked at exim log and seen every notification going to me had the following error:

SMTP error from remote mail server after MAIL FROM:<odjt@mixmaster> SIZE=8943: host hutterweb.com [173.248.187.5]: 550 Access denied - Invalid HELO name (See RFC2821 4.1.1.1)

The problem is my host name wasn't set as a fully qualified domain name. Simply changing the host name to mixmaster.ourdjtalk.com instead of mixmaster fixed the issue.

Hope it helps anyone who has come across the same issue.