MailWasher Pro 6.1

Reviews say MailWasher Pro 6.1 is the best aggressive spam filter choice because it uses multiple spam-fighting technologies, including whitelist, blacklist, database and learning filters, to sort email before it reaches your inbox. (There's also a free version that gets good reviews, but it works with only one email account per computer and lacks some filters.) Reviews say the paid version does a good job after you program it to filter out what you consider spam, but some legitimate email is going to be weeded out because MailWasher Pro is very aggressive. Most reviews say it's easy to use after a period of adjustment. One downside is that if you need to call the New Zealand developer, there's no toll-free number.

We found the best ratings at About.com, where Heinz Tschabitscher rates the free and paid versions of MailWasher in separate reports. The weakness of these ratings is that Tschabitscher doesn't detail testing methods. A review on TechSupportAlert.com deals mostly with free versions, and a review on WhichSpamFilter.com appears to be about an older version of the paid software. That's also a problem with user reviews on CNET; comments about every generation of MailWasher are lumped together, so the overall score doesn't mean much. You'll need to read the most recent user reviews, some of which indicate there's a bit of a learning curve for both the program (you have to teach it what you consider to be spam) and for the user.