postfix sends but does not receive

[Bob]

I am using postfix on an Ubuntu 16.04 system. I have also installed 
dovecot as my mail server. I am able to send mail, I am also able to 
check my mx setup from outside my domain (mxtoolbox) and it tells me 
there is only one issue with a banner mismatch in my reverse dns. The 
problem is I cannot receive mail. The system returns a "user not found" 
or "user unknown" message in the logs. I checked my home directory and 
there is a Maildir in that directory. I do not have virtual mailboxes 
set up. Any help would be appreciated.

Bob