Getting rid of Postmaster Notify

[Andrea Cogliati]

Guys,

Sorry to bother you with something that could really be completely off
topic (sendmail configuration, probably) but I cannot figure out the
solution myself.

I recently deployed MailScanner 4.14 on a Cobalt RaQ3 acting as a mail
gateway for an Exchange 2K server. Everything went really fine, even if
I'm kinda Linux newbie (thanks Julian and all you guys!!!!) and now my
installation has been working smoothly for a couple of weeks. The only
annoying issue is that the root mailbox on the gateway is filling up
with Postmaster Notify messages: usually they are User unknown errors
due to returning Invalid recipient messages to non existing spammers. As
far as I understand from Sendmail documentation, I should get these
messages only with PostmasterCopy option set (am I missing something
here?) and I checked my sendmail.cf file and I don't have this option
set.

The questions are:

Who is sending me those Postmaster Notify messages?
How can I get rid of them?

Thank you in advance for any help. Ciao,

Andrea