PHB has been proposing on the MXCOMP list that if 2821 does not match
2822, the MUA should put up a red flag.
I think this is a brilliant idea, because it gives receivers something
they can comprehend: if it's a mailing list message, they don't mind the
red flag, but if it's claiming to be from eBay, they should be
suspicious.
The only thing I can say is that I'd hope it is more informational than
yes-no in a good UI:
From: joe(_at_)example(_dot_)org, transmitted by
list(_at_)example(_dot_)com
instead of
From: (Red flag) joe(_at_)example(_dot_)org
I think this is a good, good practice (In fact, it codifies how I verify
emails already -- I read the from, if it looks bogus, I check the
headers, and glance at the Received: lines to see if there's something
valid in the chain or not.
Ari