I am getting "User unknown in relay recipient table" when sending mail from an outside account to a few internal accounts.

I am getting the following error "User unknown in relay recipient table" when sending mail from an outside account to a few new accounts in my domain.  The difference in these accounts from the accounts that are working are, the user accounts are in a child domain, they are new to the domain.

I have no issues delivering mail to these accounts within the same exchange org or with another exchange server with an SMTP connector.