D'oh. Just sent myself another test email and everything looks a-okay.
But now I know more specifically what the problem is. Thanks so much for your help.
I'm going to research fixing SELinux, but please let me know if you have any guidance to share.
Just disabled selinux, still experiencing the same issue:
ERROR: Could not complete request.
Query: SELECT "INBOX"
Reason Given: Unable to open this mailbox.
Thanks for taking the time.
What do you suggest, next?