The usual measures with these guys wouldn't necessarily do, because:
- Blacklisting the sender, which may even match against the wrong address, might cause SpamAssassin's Bayesian filter to start filtering legit announcements.
- From prior experience, service providers tend to favor their own paying customers when it comes to security or net etiquette issues (in general, ToS violations) and make it difficult for outside parties to get anything done about them (Time Warner Cable, I'm talking to you!).
In light of that, I decided to do things my own way:
220 caerleon.us ESMTP Sendmail 8.14.2/8.14.2; Mon, 5 Nov 2007 13:31:03 -0500
250 caerleon.us Hello localhost [127.0.0.1], pleased to meet you
501 5.0.0 Go away, you dumb fuck
Being a server god has its perks :-)