[Techtalk] sendmail configuration -> rejects for unknown user

[Rudy Zijlstra]

Hello,

I am trying to find a solution to the following problem:

If i understand correctly, the normal processing for unknown recipients 
is as follows:

- sendmail receives, checks intended for local machine and accepts
- sendmail passes on to local mail delivery (cyrus in this case)
- cyrus detects user does not exist, creates error
- cyrus passes error message to sendmail
- sendmail sends out error message

The problem with the above is with spam. With spam this results in 
spurious error messages to postmaster, as well as to unsuspecting 
addressees (the legal addresses used by spam senders (not their own of 
course)).

What i would like to do, is teach sendmail to check whether the local 
recipient exists, and refuse if not. I know it is possible, but after 
several hours of searching i still have not been able to find how to do 
it. Can anybody give me some pointers  on this one?


Regards,

Rudy