On Mon, 12 Sep 2005, Dick St.Peters wrote:
To send mail to someone, you had to know how to get it there, usually
by routing it through a series of gateways. As mail traversed the
specified path, each gateway extended the reverse path by moving
itself from the forward path to the reverse path. The reverse path
was then given to the next hop. For internet email, this was the
purpose of the MAILFROM. A typical MAILFROM might look like so:
"@gateway1,@gateway2:user(_at_)host3".
Yes, most of us understand that, and there was a campaign to
resurrect those deprecated routes. That would allow forwarders
to pass SPF (which would only check the immediate sender) but
still be compatible with non-SPF aware receivers (which the RFC
still requires to parse and ignore the deprecated route).
The SRS hack basically accomplishes the same thing - but with some
security to prevent spammers from sending DSN spam to a forged
reverse path.
Resurrecting the deprecated reverse route *still* appeals to me:
a forwarder can still sign the local part to prevent bounce spam.
But those wiser than I declared that undeprecating an RFC is
well nigh impossible. So - we put the reverse route in the
localpart instead (well, as much as will fit - ugghh).
On my TODO list is to experiment with using the deprecated reverse
routes instead of SRS. I'm curious how many MTAs fail to at least
parse and ignore the reverse route per RFC.
--
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.
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