Caretaker Antispam is an interesting spam filter that offers some worthwhile benefits over competing products.
You don't have to spend time training Caretaker Antispam to best recognise the junk in your Inbox, for instance. Its rules are managed centrally, by the program's authors, allowing them to quickly respond to the latest spam outbreaks without you having to do anything at all.
Caretaker Antispam also offers multiple layers of protection to keep the maximum amount of emails out of your system. It can analyse phrases and images, uses heuristics and statistical models, can recognise dangerous links, phishing messages, PDF spam and a whole lot more.
And compatibility is excellent. The program runs on every version of Windows from 2000 upwards, both 32 and 64-bit. It works with Outlook, Outlook Express, Windows Mail, Thunderbird, The Bat! and IncrediMail. And the authors have taken care to ensure that it shouldn't clash with other spam filters, so you should be able to add it to your system without any issues - just install it as an extra filter to whatever you're running already, and see if you notice any improvements.