Thanks for the clarification . . .
Do you have greylisting enabled?
If so, set your timing to the following:
and then do an initial test, and retry about two minutes later.
You can also send me an e-mail with your domain name and I'll take a look at it from a couple of other tools I use.
Phone: (224) 444-0169
E-Mail and DNS Security Specialist
Network Security Specialist
Customer Service Portal: https://portal.chicagonettech.com
Security Blog: http://networkbastion.blogspot.com/
Web and E-Mail Hosting, E-Mail Security and Consulting