Stuart D. Gathman writes:
The recivier *already* knows whether the message has been forwarded,
because they set up the forwarder! If the recipient is so disorganized
that they have lost track of their aliases (or an ISP has no mechanism
for users to enter them), then they can't (correctly) reject on SPF fail
(unless they don't care about those old forgotten aliases bouncing).
Don't be so naive. "Recipient" and "receiver" aren't the same. A
recipient may know his or her mail is being forwarded, but the
receiver mail system that is supposed to make a decision before DATA
usually has no idea what mail is being forwarded to it and what isn't.
I run one of the world's tiniest ISPs, but I still receive mail for,
and send mail from, hundreds of users with hundreds of domains.
Dozens of those users have their mail forwarded from here to other
mail systems - or to here from other mail systems. A mere handful of
those users with forwarded mail are savvy enough about how mail works
to know their mail is forwarded. The rest have simply asked to get
their mail at some preferred email account, and been told "Yes, we can
make that happen."
Two days ago I got a call from a local artist whose domain and email
we host. She was calling from a distant gallery doing a showing of
her work, and she wanted access to her mail. On looking into this for
her I found her mail was being forwarded to her local cable internet
email account by a .forward file put in her directory by somebody in
1998. It was most definitely not put there by her - or by us. She
wouldn't know how, and we don't use .forward files. It was probably
put there by the consultant who did her website.
As for forwarding to the cable internet service, getting them to
whitelist a small competitor is vastly less likely than getting them
to give a customer a PTR record, and we know how unlikely that is. So
forget all this nonsense about recipients whitelisting forwarders.
For the overwhelming majority of recipients it just ain't gonna
happen.
In the real world, most of the advice here on how to overcome various
problems with SPF essentially comes down to "Don't use SPF", which is
strange for group of supposed SPF advocates.
--
Dick St.Peters, stpeters(_at_)NetHeaven(_dot_)com
Gatekeeper, NetHeaven, Saratoga Springs, NY
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