Greg Connor wrote:
[MSA]
you should substitute a known return path associated with
that client, or reject the message.
My bet is that most ISPs do not do this...
2 of my 3 mail providers do something like this:
One is a simple SMTP-after-POP mailer, and I can only use the
MAIL FROM matching my POP3 user name (with the IP of my last
POP3 login of course).
The other is mailto.t-online.de with millions of customers.
They use RADIUS and rewrite both MAIL FROM and even the From-
header (ok., the latter is not exactly covered by RfC 2476 ;-)
Catch-all addresses would be interesting...
My 3rd mail provider, and that's why I'm interested in SPF.
I can still use corresponding From: headers with the 1st resp.
corresponding Reply-To: headers with the 2nd mail provider.
Bye, Frank