The statistics are startling: Internet security experts say most email -- estimates range from 70 percent to 95 percent -- is actually spam -- mail that's unwanted, unsolicited and/or dangerous. A typical inbox doesn't contain that amount of junk mail, though, because most spam is blocked before it ever reaches the inbox. ISPs and large companies use expensive hardware spam filters, while large web-based email services like Gmail have good results with collaborative filtering, where users identify spam emails. Major email reading software -- such as Microsoft Outlook, Windows Live Mail and Mozilla Thunderbird -- also comes with anti-spam filters.
Thanks to those efforts and increased anti-spam capabilities in Internet security software, finding current reviews of standalone spam filters (also called spam blockers or anti-spam software) is getting more difficult. If your email provider's spam filters are nonexistent or ineffective, however, a standalone spam filter can help clear the junk out of your inbox. Experts have highlighted several programs as standouts.
Experts say that purchasing a full-fledged Internet security suite might not give you the most protection against every type of security threat you might face online. But they add that most provide at least adequate protection against Internet perils. For many users, they are also easier to set up and use than a collection of separate security programs, such as antivirus, firewall, anti-spyware and a spam filter. Most Internet security suites include all those security components, and several offer extras such as parental control capabilities.
For those who prefer the ease-of-use that an Internet Security Suite can provide, most reviewers say that Norton Internet Security 2012 (*Est. $70), which is covered in our report on Internet security suites is among the best choices. Its spam filter rates very highly; in PCMag.com's testing, Norton doesn't flag a single legitimate email as junk and it blocks significantly more spam than any other Internet security suite reviewer Neil J. Rubenking has evaluated.
But as effective as Norton is at blocking spam, Rubenking reports that Cloudmark DesktopOne Pro (*Est. $20) is better. Most experts agree that the program -- a refresh of the well-regarded Cloudmark Desktop -- is the new king of the hill for spam filters. While most spam filters work only with email that supports the POP3 protocol, DesktopOne blocks junk mail sent to IMAP, Microsoft Exchange and web-based mail, too. The program runs as a standalone Windows service and keeps tabs on protected accounts even when your email reader isn't open. Reviewers say that installation is a breeze and the community-powered filter is very effective. Rubenking says the program allowed only 2.6 percent of junk email into his test inbox, although TheTechHerald.com reports that the program loses efficiency when massive amounts of messages are scanned at once.
The free Cloudmark DesktopOne Basic software offers the same strong, ad-free spam fighting capabilities and robust IMAP/POP3/Exchange/web mail support of its premium counterpart -- but only for a single email account. The Basic version also loses some of DesktopOne Pro's bells and whistles, such as on-demand scanning, the ability to schedule an automatic purging of the spam folder, technical support from Cloudmark and scanning of emails that are more than a week old. Nevertheless, Rubenking gives both versions a PCMag.com Editors' Choice award for best spam filter.
If you're looking for a free spam filter that supports more than one email account, most experts recommend considering Spamfighter. A paid Spamfighter Pro edition (*Est. $30) is also available. Like Cloudmark DesktopOne, Spamfighter taps into community reports and combines a high blocking rate with a low false positive rate for effective anti-spam protection. The software does have a few drawbacks: Unlike DesktopOne, which supports virtually every type of email, Spamfighter is limited to protecting POP3 email, and it can do so only in Outlook, Outlook Express Windows Mail, Windows Live Mail and Thunderbird. Additionally, the free version is limited to 100 custom whitelist/blacklist entries, and it includes ads in its mail client toolbar and inserts a text ad into outgoing emails.
Spamato and POPFile are two other well-regarded free spam filters, but experts warn that casual users may have trouble training and maintaining these more-technical programs. They also aren't updated regularly, and most reviews are now older.
If you have a computer with limited resources or use an email client or operating system with limited support from traditional software-based spam filters, experts recommend using a web-based spam filter such as ClearMyMail (*Est. $25 per year), a U.K.-based service that also services U.S customers. Incoming email is filtered by the service and deposited in your inbox when you go online. Because it protects the email subscription rather than an individual computer, ClearMyMail works with any operating system, including Windows, Mac, Linux, smartphones and BlackBerry devices. It also works with any POP3 email client, but not webmail accounts unless they offer POP3 support.
Experts say setup is simple and the "18-stage filtration process" is almost perfect at blocking spam while allowing legitimate mail into your inbox. In fact, ClearMyMail will return your monthly fee if you receive a single piece of spam in your email. However, while software-based spam filter subscriptions typically protect all of your email accounts, the web-based ClearMyMail is $25 per year per email account, which could add up quickly if you need protection for several users.
Given the scarcity of spam filters and spam filter reviews, finding useful information requires casting a wide net. PCMag.com, Web User and About.com each cover several programs, although some reports are dated. PCMag.com's exhaustive testing-based coverage outshines Web User's and About.com's short reviews. Virus Bulletin provides helpful bimonthly anti-spam certifications. TopTenReviews.com offers its picks for the 10 best premium programs, and Download.com contains extensive user reviews. PC World, TheTechHerald.com and PC Advisor all offer helpful one-shot reviews of specific software.