Name resolution in FreeBSD/Postfix

Folks:

Trying to configure Postfix to route local mail (internet is later). 
During a telnet conversation with Postfix to send it mail for a local 
user, it chokes on paulf@localhost recipient, with a 451 4.3.0 error. 
This is my user, and it's in the /etc/passwd file. So I don't understand 
why it doesn't understand the recipient email address. And yes, 
localhost is 127.0.0.1 in the /etc/hosts file.

Can anyone enlighten me?

Paul

-- 
Paul M. Foster
Personal Blog: http://noferblatz.com
Company Site: http://quillandmouse.com
Software Projects: https://gitlab.com/paulmfoster