At 16.47 09/05/2006, you wrote:
Easiest thing to do is add a .qmail file in the postmaster directory
stating '|/bin/true delete' to scrap the message [just sets it as
deleted by default].
Now I'd imagine the main frontline you'd want to investigate is
chkuser.c if you use it. By line 567, it's got a user and domain
split. Under case 10, it actually does the user check, so just have
it test the user for 'postmaster' and return a failed 'user does not exist'.
It could be more easy to set the BOUNCE_FLAG on for each postmaster,
and message will be rejected.