MX, non-existent hosts

Hi guys, I'm having a very strange issue and I'm not sure where it's originating from. I just migrated a friend + email account(s) to my reseller account as my first "client" (Yay!!) Set up DNS according to the below: A record (mail.XXXX) pointing to the IP of the server MX record (XXXX) pointing to (mail.XXXX) with a priority of 10. When I've tried to send an email from my reseller Cpanel (attached to my domain. etc) I get non-delivery according to the attached. Is it possible because we are in the same "data center" that my email is finding the server before leaving the local network? Is there another way to set this up? it's the same as how I've set my domain up through Cloudflare and it works flawlessly. Thanks in advance. Josh.