In the week since I switched this new blogging system on, I've had more than fifty trackback spams ... and no genuine trackbacks at all. So I'm switching trackbacks off completely. (I'll review this decision in a few weeks time, but right now I don't see why I should enable a feature which seems to only be used by spammers. Even though the built-in spam filtering caught all of them, I can't be arsed riding herd on it.)
Interestingly, there have been no attempts at comment spamming — or none that have got through the various spam detector plugins I've installed.
Meanwhile, my email continues to attract 300-500 spams per day, and a total of 2-3000 per day for all ten or so users on my server.
I've long since disabled Trackback on my site; it was being abused so much by spamming scum that it wasn't worth the effort any more.
Whereas comment spammers would hit me with at worst a dozen or so spams at once, the trackback ones typically hit me for hundreds at a time.
Trackback was a nice idea, but spamming has effectively killed it.
If you're operating your own mail server (or can get your admin to do this for you), you might find that "greylisting" will help cut back spam. Greylisting takes advantage of the fact that most spammers are using crappy mail transmitters which come and go quickly. When you receive mail from a new address for the first time, your mail server simply says "come back later" and shuts down the connection. This is acceptable SMTP behavior. Most spammers will never come back later.
One of the nicest features of greylisting is that the spam is never even received, and doesn't eat into your bandwidth.
We've been using it for quite a while. It's not a panacea, but it's been one of the best defenses we've used.
I had a dream of an Asimov story with the tag line 'Step right up and kill a spammer' in one of the great one's ever so convincing fun fairs. Then I woke and remembered it was 'Step right up and kill a woman'. Yes. Well. Exactly what DO you say to that? Still, my dream was nice. Do you think spammers are charvas when they're not at work?