Before getting a linode I used to use a OpenBSD mailserver.

OpenBSD came with something called spamd which can be used to tarpit incomming mail connections based on an IP list. I used spews as my IP list plus my own personal lists, with overriding whitelists for every IP I got regular non-spam mail from.

I would like to do the same for my linode.

There are hundreds of ways of filtering mail, or dropping mail connections. I don't want these, I want to tarpit the spammers. Anyone know how to do this with linux?

I'm sure I can figure out the iptables bit, but I still need the spamd daemon to deal with connections from offending IPs.

I think it depends on what MTA your using... don't ask me which are capable though... I do know that I'm currently using qmail along with spamd and spamassassin, but I barely know how it's all configured.

I don't think the MTA has anything to do with it. Or at least it doesn't on OpenBSD.

Packet filter redirected connections to port 25 from known netblocks before the MTA even got wind of them. I can do that bit with iptables, What I don't have is a daemon to do the tarpitting after the connection is redirected.

I could use DNS blacklisting to refuse connections, but I don't want to refuse them, I want to waste their resources.