Hotmail Having A Problem With US Army Email Addresses?

It is not a rant, but a kind of “I don’t get it” thing.

I have a friend who has an “” email address and Hotmail continually tells me that “The sender of this message,, could not be verified by Sender ID. Learn more about Sender ID.”

And yet, my wife, who had a similar (Air Force) email address until recently, “,” never had her emails tagges with this.

I probably should just write Hotmail, but they are not as much fun as you all are. Any ideas why one military email address is fine, and the other one Hotmail “cautions” me about?