If you haven't caught this yet, you probably won't get this, but the blackhole 
lists at osirusoft.com are blocking *.*.*.* to make the point that the 
service is shutitng down in response to a major DoS attack.

http://slashdot.org/article.pl?sid=03/08/27/0214238&mode=nocomment&tid=111&tid=126

It seems to me that there are better ways to do this.  I lost a lot of mail 
over the three days before I caught it, and I would think legal action 
against whoever was attacking your sight would be more satisfying, but I 
guess he just doesn't have the resources, and The Man dosn't care about him.