Guðbjörn,
I think that the "registration" oriented authentication mechanisms (spf, rmx, lmap, etc.) can be useful only when the authenticator is the hosting network provider, rather than a message author.
GSH> I think widespread use of SPF will gut the major sources of spam. Well, it will gut a great deal of email mobility and third-party services. It will probably have no meaningful effect on actual spam. For example, as you note: GSH> Then, of course, the spammers will find other ways... That means that _at best_ MTA author registration schemes, like SPF, are tactical responses. The problem is that they cause a _strategic_ change to the email semantic model; and the scaling effect of its administration is really quite terrible. Pretty massive effect, for such a short-term benefit. Not to mention that, on the Internet, it is never possible to deploy anything in a short-term time-frame. And, oh by the way, all SPF tries to do is to authenticate the From field. Forgive me for not being reassured that wide use of SPF will merely mean that the spam I get will have a valid From field. d/ -- Dave Crocker <dcrocker-at-brandenburg-dot-com> Brandenburg InternetWorking <www.brandenburg.com> Sunnyvale, CA USA <tel:+1.408.246.8253>