Spam filtering software recommendations requested

[glc]

I have a customer (a law firm) who has wound up on a bunch of junk lists. They are receiving literally hundreds of spams a day. I need to find spam filtering software that works with Outlook Express (not Outlook). Their mail host does not offer any server side filtering, and the logistics of changing hosts are really not feasible at this time. A good portion of this spam is from the same domain, but a simple blacklist won't do the job, it needs to have some kind of intelligent filtering too. We don't want something (like Qurb) that's whitelist based. We need something that can be installed on each workstation, a centrally located solution won't work because they don't run their own internal mail server, and it must be user friendly (i.e. users without a clue don't have to learn any procedures).

Thoughts and recommendations, folks? I'm especially interested in input from people that are actually using what they recommend. Thanks!

[pam123]

Last year, before I switched to Thunderbird, I had a spam problem that I solved with Spamfighter, the free version.
I don't know how a law firm would feel about the whole "community of users" thing (it's similar to what Micorsoft is using in the beta version of their anti-spyware) but it certainly worked.
Info about the Pro version for businesses is here : http://www.spamfighter.com/

It does include a whitelist but it's not only a whitelist filter.

[glc]

Thank you, Pam - I just sent them the info, and the hosted spam filter actually may be what they need, no configuration hassles, pay them the fee and they take care of everything.

[pam123]

Glad it was useful.
It was a fellow pcmech'er who pointed me in the right direction back then but he sent me an e-mail and I've had a drive crash since then so I have no record of who.