How to Buy a Spam Filter

Choosing a spam filter

The simplest spam promotes some product or service -- occasionally legitimate though unsolicited but most often illegal or gray-market items, including drugs marketed as sexual performance enhancers. More complex schemes are designed to trick users into revealing sensitive personal or financial information, a technique known as phishing. Spam can also be used to distribute viruses and other types of malware. As anti-spam tools grow more effective, spammers turn to new techniques to bypass email protection.

First and foremost, an effective spam filter has to stop spam from landing in your inbox. Spam filters shouldn't misidentify legitimate email as spam very often, either. Here are some additional considerations:

• Verify compatibility with your email program. While support for Outlook, Windows Live Mail and Mozilla's Thunderbird is fairly widespread, a lot of software-based spam filters aren't compatible with alternative email clients like Eudora, IncrediMail or the email client built into the Opera web browser. Web-based spam blockers like ClearMyMail can work with almost any email client.

• Not all spam filters work with all services. Before paying for anti-spam software, make sure it is compatible with your Internet mail provider. Many email providers -- including Hotmail, Gmail and most Internet service providers -- now offer POP3 to allow users access from standalone email clients like Outlook. Most spam filters support POP3 email. However, finding a spam filter that protects web-based email or the IMAP mail protocol is more difficult. For example, the only one of our Best Bet picks that supports IMAP and web-based email is Cloudmark DesktopOne. Do your homework before you drop your cash.

• Check to see if you already have a spam filter. Most major Internet service providers and email services (like Gmail and Hotmail) have fairly effective spam blocking capabilities baked in by default. Some applications, like Microsoft Outlook and Mozilla Thunderbird, have additional spam filtering options for junk mail that sneaks past service providers. Spam filters are also a part of many integrated Internet security suites. Reviewers say your best bet is to try the tools you already have before buying separate anti-spam software.

Do you need a spam filter?

While antivirus, anti-spyware and firewall applications are essential components of computer/Internet security, spam filters are not. Most commercial spam is time-wasting but not harmful, and most spam containing infections is dangerous only if you open the message or its attachments. Most major web browsers, email clients, and antivirus and firewall programs protect against phishing scams. If you use Gmail, experts say its excellent spam filters make using a second anti-spam program largely unnecessary.

Time investment is another consideration. While some spam filters offer strong out-of-the-box protection, many anti-spam applications require about a month of additional training to learn what you consider spam and what you consider legitimate mail. With training, the programs become progressively more effective at filtering. While no anti-spam programs require that you review quarantined messages, you are likely to want to know if your program is blocking legitimate messages. Base your decision on whether the time commitment to use an anti-spam program is greater than the time you spend deleting spam.

In the reviews we found, even the best spam filters block one or two legitimate messages out of every 100 messages received. If those messages are important, that might be one or two too many.