"The email message's originator address is taken from one of the
following five sources, shown in decreasing order of preference:
1. Resent-from: 4. Sender:
2. From: 5. Envelope From:
3. Resent-sender:"
What about it?
The PRA algorithm isn't arbitrary; it's based on the RFC(2)822
definitions of the fields.
The above algorithm makes no sense to me. The fact that someone has
used it for something in the past is not a justification for using it
here.
-roy