[sf-lug] postfix config question

[jim stockford]

on a Red Hat 6 box (yes, ancient, pre Red Hat 9 OS), our Postfix
email server is sending out an "unknown user" reply to inbound
mail from spammers who're trying xxxxx at ourjoint.DOM

Unfortunately, this is generating an unacceptable amount of traffic
back to the Speakeasy server. They suggest that when our server
gets mail for an address for a user that doesn't exist on our host,
our Postfix server simply doesn't generate a reply.

Which configuration setting(s) in /etc/postfix/main.cf to change so
that it does this? or what alternative approach to make speakeasy
shut up?

jim