Best spam filtering service?

I have a client with their own domain who are getting inundated with spam - hundreds of messages per day. I’d like to route their mail through a commercial spam filtering service that would have a large blacklist, but would also allow the uploading of a whitelist to ensure their customers can get through.


Seriously? Nobody has an opinion?

Google Apps is perfect if she has her own domain. And free for fewer than 51 people.

Google Apps is a spam filtering service? They already have hosting, and all their e-mail clients are pointed to

I’ll have a look.

It’s not a spam filtering service per se, but it has very good spam filtering. The person can keep his domain, and just update the mail handling records and email clients so that Google Apps handles email, instead. Then you have an excellent gmail-like web interface when wanted, and perfectly good IMAP service for proper email clients, and even better Microsoft Exchange PIM services (Activesync) for devices that support that.