We just don't know. The Washington Post didn't say.
A crime may or may not have been committed.
I'd be quite surprised to find the Post 'reporters' weren't the receiving end of the mails--considering the freepmails were all posted by MD4Bush. We DO know that MD4Bush has recently been banned. Circumstantial evidence is still evidence, and I can't think of any OTHER way the freepmail would have been relayed to the media. And as MD4Bush was the party to the conversation most likely, there aren't any crimes committed under that law, I bet. Maybe a state or some other law (wasn't MD where the cell phone stuff took place a few years back) but doesn't look like this one.