The original SPF that most of us read a bunch of years ago stated that a record starting with "v=spf1" should apply to the SMTP MAIL FROM.

SenderID says a record starting with "v=spf1" applies to both MAIL FROM and the "Purported Responsible Address," which is dervied from message headers via a specific algorithm.

The current "Classic SPF" spec says that "v=spf1" applies to both MAIL FROM and to HELO or EHLO.

It's okay if you don't understand this one; it was written for a fairly specific audience.

To -all, or not to -all--that is the question:
Whether 'tis nobler on the net to suffer
The questionable results of outrageous hyperbole
Or to take voice against a sea of edge cases
And by opposing, expose them. To forward, to resend--
No more--and by a forward to say we forge
The message, and the thousand natural headers
That mail is heir to. 'Tis a featureset
Devoutly to be preserved. To forward, to resend--
To resend--perchance by lists: ay, there's the rub,
For in that resending by lists what change may come
When we have altered this delivery path,
Must give us pause. There's the respect
That makes calamity of so long kludged.
For SMTP did bear the whips and scorns of time,
Th' spammer's wrong, the proud geek's RFC,
The pangs of despised love, the law's delay,
The insolence of office, and the spurns
That patient merit of th' unworthy sender,
When he himself might his quietus make
With a new protocol?

Okay, I'm kinda losing it here. *grin*

I was poking around a bit, and noticed that Microsoft still isn't publishing SenderID pra records anywhere -- not for hotmail.com or msn.com (which I set up while I was there), but also not for microsoft.com or exchange.microsoft.com.

This seems...ironic, don't you think?