Screaming Penguin - Source Does Matter

There is a new draft RFC out called SMTP+SPF (Sender Permitted From). Oddly enough, it sound very much like what I have said we need for a while, minus some IP spoofing proof encryption. Basically, the system works like this:
You used the "TXT" DNS record on a reverse lookup to list a group of IP addresses that are auhorized to send email with a "from" address in your domain, thusly:


*.133.149.66.in-addr._smtp_client.example.com. TXT "SPF=allow" *.149.66.in-addr._smtp_client.example.com. TXT "SPF=allow"
*.66.in-addr._smtp_client.example.com. TXT "SPF=allow"
*.in-addr._smtp_client.example.com. TXT "SPF=deny"


This gives the receiver and easy was to veryify that an authorized SMTP server sent the message. Granted, this will mess up the way I use SMTP personally a bit, but hey, whatever works at this point.
SpamAssasin will be implementing SPF with version 2.70.