On Wed, 17 Aug 2005, Seth Goodman wrote:
The only things we've lost by insisting that the From: or Sender: domain
matches the MAIL FROM domain is one anonymizing mechanism and a clear chain
of remailing events in the rare case that intervening MUA's or MTA's
actually support this. We still have the Received: headers, so the path
information is not lost. In a time when we have to authenticate the origin
of messages in order to assign responsibility for abusive behavior,
trivially achieved anonymity may be a necessary casualty.
This is actually a good idea. It could be called 'Sender-ID Lite'.
By matching only domain, MAIL FROM signing techniques continue
to work. I would suggest that MTAs should not reject based on From/Sender
domain not matching MAIL FROM, but that MUAs should simply highlight
a From or Sender that doesn't match with "POSSIBLY FORGED" warnings.
If MUAs don't do that, an MTA could add "[POSSIBLY FORGED]" to the Subject,
or otherwise flag the mail without rejecting it in a manner visible via
the MUAs behind it.
Question: do we require an *exact* domain match? What about
MAIL FROM <foo(_at_)mx1(_dot_)bar(_dot_)com> and From: <baz(_at_)bar(_dot_)com>?
I will start doing your proposed check in pymilter and logging possible
forgeries. This should give us an idea of how feasible it is.
Quick, someone with $100 and lawyers fees to spare, file a patent for
the open source patent pool before some jerk sends you a cease and desist
letter for your own invention.
Stuart D. Gathman <stuart(_at_)bmsi(_dot_)com>
Business Management Systems Inc. Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flamis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.