Back in October 2004, Google started playing with Yahoo's Domain Keys anti-spam technology. I'm not sure what ever became of that test. What I do know is that sometime on Saturday March 4, (2006), Gmail started adding Domain Key data to the headers of Gmail.com-generated email that wasn't there before. Here's a whole new text block that didn't appear in the header of Gmail.com-generated emails that arrived in my inbox prior to 3:30pm ET on 3/4:
=== BEGIN TEXT BLOCK =====
DomainKey-Status: good (test mode)
DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws;
=== END TEXT BLOCK =====
Maybe this isn't news. Or is it?