[selowitch]

Can anybody recommend either a web hosting service that does a good job blocking spam (and also offers PHP/MySQL) or an aftermarket antispam application that you can deploy on a web/mail server?

[Macola]

As an alternative to either, try SpamCop. Your money will go to a worthy cause, and you can (if you choose) report spam as well as blocking it.

[turtle777]

www.dreamhost.com and SpamAssassin.
Works brilliant on all my IMAP accounts.

You can either use the pre-configed SA, or install it yourself. You have full SSH access to your account, so you're the king in your domain.

-t