Actually it came from Elias in some other place, Lee Ann just reposted it. :-)

The unknown user bit is interesting, but more and more spammers are trying username scans. If this is work, I'm not quite as surprised, if it's your home machine, then that's quite large. You might find that those things are bounces, too, with your domain spoofed. I see many of those @colondot.net. They're often quite plausible local-parts, too.