Personally, I pay for a provider with bullet-proof spam protection. In the average month, I might get as many as 20 or 30 spam emails delivered to my account. Of those, 80% are delivered to my "Junk Mail" folder, with very few false positives. I get, at most, 4 to 6 junk mail messages in my Inbox.
I've never known anything like this service. It's like rediscovering email for the first time. Whenever I talk about it, I sound like an advert for the company. I'm not in any way careful about who I give my email address to, or where I use it on the net. The server simply kills email from known spam sites silently, without it being delivered to my account. Suspected spam is tagged as such, and delivered to my Junk Mail folder, and mail from my contacts is whitelisted so that it is never flagged as junk.
For this service I pay 20 dollars a year. The site is
http://www.fastmail.fm/ and they offer IMAP-4 and POP-3 interfaces to mail accounts, which means they will be compatible with whatever software you prefer to use. Since you mentioned that you'd prefer freeware, I'm sure this probably isn't really of a great deal of use to you, but it is the ultimate protection from spam, as far as I know.
Jam it back in, in the dark.