no To: header in emails

[Eric Wood]

I'm using sendmail 8.11. How do I get emails that contain no To: in the
header?  I do get this at the top of the emails:

Received: from
 by
 for eric at interplas.com


Now I'm going to do this:
:0
* !^Subject:
/dev/null

:0
* !^To:
/dev/null

I just don't understand how mail still gets delivered.
-eric wood