restricted aliases

[Chris St Denis]

I need to add support for (multi-recipient) aliases that are only able 
to receive messages from selected users.

I was initially looking at mailman or majordomo, however from what I 
understand of them, they authenticate only on the from address so it 
looks like it would be easy to forge. (Correct me if this is wrong).

I also thought of smtpd_restriction_classes however that is also subject 
to easy spoofing and the documentation even says "Postfix restriction 
classes aren't really the right solution"


So I am wondering. What IS a good way to do this. Optimally, I would 
like to restrict based on the SASL username.