Did you get your answer?I always hate it when I come across a thread that matches my needs, reading through pages and pages of posts, just to find someone post "Solved it thanks guys!" with nothing about how it was solved. I don't want to be that guy.
Inside the Cpanel > MX settings there are option buttons, check the one that says LOCAL.
Now, I did that and still does not work for me. I continue to have issues sending out email.