The best I can suggest is installing postfix-doc, and then looking through /usr/share/doc/postfix (but not /usr/share/doc/postfix-doc, wtf?), if you haven't already ...

I'm trying to setup a Postfix server, but I can't seem to get the mailboxes configured correctly. Every time I try to test sending an email using telnet, I see errors in the Postfix logs.