Mark writes:
SPF is inter-MTA based, and requires no changes to email clients
whatso-frickin-ever.
The first time I looked at SPF was because I wanted to ensure that an
email client was okay. Specifically, I wanted to check outgoing mail
from a roadwarrior machine, and warn the user before sending any mail
that would likely fail.
That job wasn't so easy. Not so easy.
Arnt