hosts.deny SMTP
SMTP: 123.456.789.123
but that didn't seem to do anything. I did a quick search on Google but didn't turn up anything in the first couple of pages.
Note: I'm not trying to ban a spammer, this is a long-time customer who for some reason has started connecting to the SMTP server several times a second and it's causing problems. I don't want to list their IP under ALL: in the hosts deny file, because a) I don't think they're aware of what's going on (no replies to our e-mail yet), and b) they're a large business that depends heavily on e-mail, and I don't want to prevent them from downloading their incoming e-mail. They're actually not sending e-mail, just making connections to the SMTP server (why, I have no idea).
