Sieve Scritp: How to recognize multiple sender
Sender must be ONE. When I see multiple sender this is sure fake mail
We have experimented with comparing the Return-Path and the From headers and found that it causes many legitimate emails to be flagged so we have chosen to not implement the option. With that being said, there is a SpamAssassin rule that compares the Envelope From and From domains. If you’d like, you can increase the score for the HEADER_FROM_DIFFERENT_DOMAINS rule by editing the local.cf file.
all ideas are well come.
I think email would have from header equal to sender and if not I can add some points if I want do it.
In any case one sender and one "From" must be accepted.