On Mon, 9 Aug 2004, Joseph Brennan wrote:
> The better solution would be referrals like web servers do. When
> the sender host says RCPT TO: one of these addresses, you send back
> a response stating the forwarding address, and the sender host then
> closes the smtp session. But SMTP and ESMTP do not provide for
> this!
You can't always easily do referrals -- what if a destination address
forwards to three new addresses? Or five thousand new addresses? :-)
Lots of people still run mailing lists using aliases and .forward
files.
The SPF people have proposed an extension to ESMTP called the
"responsible sender" or something like that. Let's say mail from
[EMAIL PROTECTED] gets forwarded by a machine in the domain2.net
domain. The MAIL command after forwarding would look something like
this:
MAIL FROM:<[EMAIL PROTECTED]> RESPONSIBLE=<[EMAIL PROTECTED]>
and the argument of the RESPONSIBLE parameter would be used for
SPF checking.
I'm going from memory, so probably have details wrong, but that's the
gist of it.
Really, SPF is broken in several ways, and the only way to fix it is
to add extensions to ESMTP and hope they become widely used.
Regards,
David.
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