- only allow SMTP relaying from IP's assigned to *their customers* dynamically (cross-reference Radius logs?)
I have heard that uunet and PSI don't provide enough information in real time for their POP farm ISP customers to tell the difference between their own customers and other random users of the same POP farms, much less tell which user is on which IP so they can stamp outgoing mail. Is that still true? Speaking of POP farms, the other major one is IBM -- how much real-time info do they provide? And since we're on this topic, at NANOG in Scottsdale we suggested that ISPs firewall in their users so the only port 25 connections they can make are to the ISP's own SMTP server, so the ISP can stamp outgoing mail with the actual sender ID and possibly do volume monitoring and choking. (You could either block connections or other systems, or warp them to your own servers, and you'd need provision for exceptions for people who send in a signed AUP, etc.) How far is that from being feasible for POP farm customers? -- John R. Levine, IECC, POB 640 Trumansburg NY 14886 +1 607 387 6869 johnl@iecc.com, Village Trustee and Sewer Commissioner, http://iecc.com/johnl, Finger for PGP key, f'print = 3A 5B D0 3F D9 A0 6A A4 2D AC 1E 9E A6 36 A3 47