postfix is not out of spec; one can either reject the mail at smtp or
send a bounce.  IIRC postfix queues the msg and then checks it to
avoid doing much in the listener (for security reasons).

You can add a check to the smtpd in main.cf:

smtpd_recipient_restrictions = check_recipient_access hash:/etc/postfix/access_recipients

(of course you want more there, but for illustration)


Then you need to keep access_recipients in sync.

It would be nice to have a way to generate this automatically and not
have to do the manual part, as the default operation mode.

-- 
        Greg Troxel <gdt@ir.bbn.com>