how to filter on invalid local users

[Brian R. Jones]

I'm looking a way to create a rule that will allow me to filter on 
[EMAIL PROTECTED] where invalid_user is anything that isn't in 
my alias or password files.  At the moment the only way I can think of 
doing this is to add an eval rule to EvalTests.pm, but this is obviously 
 not a preferred method.

Anyone have any other suggestions?
My setup is sitewide SA 3.0.2 MTA=sendmail 8.12.8 on RedHat 7.3 (yeah I 
know it's ancient, but it still works)

--
Brian R. Jones
Ob.  tagline:
        "I never follow the herd.
                Even when it's going the right direction."