Slapped in some marginal spam protection on my essays site about two weeks ago. It worked, briefly, but as all it did was verify that there was an MX or an A record for the submitted email address (and otherwise silently discarding the submission, as all failed "you are not spam" checks lead to), I have now instituted another.

Alas, I was a bit over-eager with the cleanup this time and I am considering putting up a static page with "commercial content archiving policy" stating that, yes, you can post spam and have it stored, at a cost of UKP 10 per day, per message. This is, of course, a more modern version of my spam archiving policy from the mid-90s (no, I received neither apologies nor money, but I did have great fun sending out a couple of emails asking for it, referencing said web page; I also know that it was adapted by some other people).