A couple of months ago I was scouting around for a spam filtering service that would act as an SMTP relay and filter out spam into a separate mailbox. The primary reason for this was so that when I’m out and about, I can download e-mail onto my SmartPhone without having 50 junk e-mail clogging it up, wasting my GPRS bandwidth, and generally masking the legitimate messages.
I didn’t have any luck with splagger - they didn’t respond to my enquiry - and everything else similar was aimed at large business and was way too expensive.
I think I’ve gone with the next best thing and I’ve been using the godaddy e-mail service for the last month or so. The great thing about this service is that you can install an application on your desktop called Spam Xploder that allows you to train the spam filters by dragging and dropping good and bad mail from Outlook or Outlook Express and it uploads the processed data to your account. This gives a Bayesian filter but on the server-side, which is just what I wanted.
One problem area in the sign-up process is that it won’t let you configure your mailboxes until you have pointed your MX records at their servers but of course once you’ve done that, you mail will bounce until you do configure them. Unfortunate but I guess designed to reduce support costs for average users who wouldn’t know an MX record if it jumped out and bit them on the nose.
One thing that isn’t clear from the site information is that if you sign up for a package including multiple mailboxes, those mailboxes don’t appear to need to be in the same domain name, so if you have a few domains and one mailbox in each then this works out well.
I’ve been very pleased with the service - if 4 or 5 messages in one week get misinterpreted as spam or don’t get caught then it is having a bad week. I just log in to the web mail every day or so to check through the filtered messages and purge them from the store. If you need something like this, I’d certainly recommend them.