I got the first completely empty email sometime late friday evening, and deleted it without investigating any further. Then I received two more Saturday morning. Now I've gotten almost a dozen, each from a different netblock around the world, and sent to different domains. The SANS NOC has seen 500+. The Internet Storm Center has gotten two queries about them.

There is some speculation it may be malware related, as in a poorly written piece of code spewing out empty emails. One other theory involves confirming known good addresses to seed a new piece of malware or spam. Is this related to Yamanner (sp?)?

Cheers,
Adrien