The (IMHO) world's best spam filter, SpamAssassin, is a tricky beast to get running under Windows due to its UNIX-focused application structure. Thankfully a company has put it together with a lovely graphical interface for use on Windows and calls it No Spam Today. To make it really useful you need to add on an extra product called SpamMover which moves all messages marked as spam into a separate folder. Easy-peasy. NoSpamToday is available with a free 10-mailbox non-commercial license or you can try it for free for 30 days to see if it works for you, but unfortunately SpamMover only works with two predetermined test mailboxes before you buy it. In total you're looking at $399 for 50 mailboxes for NoSpamToday and another $100 per server for SpamMover, so $500 for 50 mailboxes, and the best thing is that there are no annual charges for either, you get free minor updates and can buy the major updates if you decide you want them, unlike most "enterprisey" software that require an annual subscription in addition to the software price. Well worth trying.

After the last few weeks I'd like to mention, perhaps re-itterate, two reasons I particularly dislike Microsoft Exchange:

1. Information Store. Imagine having millions of messages in your inbox. Imagine all of your attachments are stored with all of the messages, including those joke emails your friends insist on sending, the daily reports your boss sends and the work-in-progress files from your outside consultants. Lets say with a small company you end up with 16 gigs of data, with a reasonable expectation that your email traffic is going to continue to grow. Now lets throw in a random data error, or maybe your version of Exchange hits a storage limit forcing you to do some maintenance. You turn off the Information Store service and start up some maintenance utilities (which are all DOS-based BTW) and groan as it takes four+ hours to fix the database. Now imagine that you had also started using some public folders so had a few hundred meg in them, all on the same drive. Now imagine your drive is 32gb in size. Now imagine that the Exchange tools need 16gb of free space to do its work on your 16gb of email data, and it must be on the same drive. Now do some maths: 32gb total - 16gb mailboxes - 300mb public storage = less than 16gb. Now imagine that after waiting for four hours for Exchange to do its thing it gets 97% finished and fails because it ran out of disk space. Now imagine having to start it all over again. Now imagine doing that during a work day for a business that does most of its communications via email.
2. Intelligent Message Filter (IMF). Available as part of the Service Pack 2 update for Exchange 2003, IMF is Microsoft's first attempt to bring a spam filter to Exchange. in comparison to every other spam filter on the planet its functionality is limited - messages get shuffled either a per-user "Junk Email" mailbox or a file-based archive, it has a basic Bayesian filter to do the grunt work, a blacklist for domains/addresses you never want to receive email from, a whitelist to.... oh wait, there's no whitelist! So despite the fact that Microsoft believes you may want to set certain addresses/domains to never send you email, it is so confident in IMF's ability to correctly filter email that it doesn't think you'd ever want to have it force addresses to be considered ok, nah that's just a silly feature that lesser products support, they don't need it. So, despite the fact that it regularly sticks good email in my junk mailbox (false positives), Microsoft doesn't think I should worry about it. Riiiiight. I should also add that for the Bayesian filter there's a whopping one configuration value for this - you set a number between 1 and 9 as to how sensitive you want it to be and that's it, no tweaking, no "be harder on people attaching pictures", nothing. Thanks, but I'll take my industry-standard, thankyouverymuch.

Rant off.