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The latest effort in the Sisyphean war against e-mail spam is a fix known as “challenge-response” systems. Unfortunately, it can sometimes do more harm than good.

Challenge-response e-mail systems work on a simple premise: Good e-mail comes from people you know, and bad e-mail from people you don’t know.

There are some issues with that idea – someone you don’t know may send you a legitimate e-mail – but the notion is innocent enough. Real humans with whom you interact on a regular basis will send e-mail you definitely want to see and read. E-mail that is generated by machines and sent to millions of recipients, you can do without.

A challenge-response system sits between your e-mail and the outside world. It scans the sender of every e-mail that you receive, and verifies that the sender is on your special list (usually called a “whitelist”).

If yes, the e-mail is let through. If not recognized, the challenge-response system quarantines the e-mail and sends the sender a short message to make sure it’s a legitimate person sending a legitimate e-mail.

Sometimes this challenge message is simply a request to have the sender reply to the message to confirm that they are a real person.

Usually the challenge message is a little more involved. It may ask the sender to answer an easy question, such as “How many kittens are in this picture?”

If the sender is legitimate, they can answer the question easily and they are added to your whitelist. If the e-mail is sent by a machine, it doesn’t have the capacity to look at a picture and tell how many kittens there are, and so the message is trashed as spam.

In theory, this is a foolproof system. You get legitimate e-mail from legitimate people, and the machines of spam no longer bother you because they can’t get past your impenetrable wall of a challenge-response system.

But challenge-response systems are not without their critics. First off, the world is presumed guilty of sending spam unless each sender is added to the special list of innocent senders. That idea doesn’t sit well with a lot of people.

Second, challenge-response systems literally add more e-mail to the already overflowing traffic of electronic messages. How can more e-mail be the answer to the problem of overflow of messages?

Lastly, the major complaint against challenge-response systems is that they’re just plain annoying. Sure it’s just a harmless question that you have to answer, but you just feel like you have to unnecessarily prove your innocence by doing it.

Besides, what if a legitimate sender just plain refuses to reply to the challenge message? Or forgets? The message sits in limbo forever.

Personally, I get a lot of people that e-mail me from all over – readers that I’ve never met before – asking questions and providing suggestions. Is it right for me to require them to respond to a challenge message before I can be bothered to respond to them?

There are a few products on the market today that use challenge-response technology to protect you from bad e-mail. For a completely Web-based service, you can try Mailblocks ( www.mailblocks.com), which features its “Challenge/Response 2.0″ technology. If someone sends an e-mail to your Mailblocks account and they are not on your personal address list, a challenge message is sent to them and they are asked to copy down a number that appears in a graphic on a Web site. Once they correctly answer that question, their e-mail is allowed through.

Curiously, if a sender is allowed through for your account, then that same sender will be allowed through on any other Mailblocks account.

If you prefer an application that works in conjunction with your e-mail client (such as Microsoft Outlook or Outlook Express), then try MailFrontier Matador ( www.mailfrontier.com) or Qurb ( www.qurb.com).

MailFrontier Matador works with Hotmail, MSN, Outlook, or Outlook Express. When Matador doesn’t recognize a sender, it will send them a challenge message with a randomly selected question such as “How many puppies do you see in the picture?” Once the question is answered, the e-mail is allowed through.

Sending a challenge message is optional with Qurb. When the feature is turned on, Qurb will automatically send confirmation messages to unknown senders. If those senders reply to the confirmation message, that sender is added to your whitelist.

While many users feel safe and protected from spam with challenge-response systems, many others are still doubtful that the technology is ready for widespread use.

Earthlink is the only major Internet service provider that has incorporated some form of a challenge-response, but it is a watered-down system that is part of their larger antispam measures.

It is clear that challenge-response does work at some levels, but ultimately, it appears to cause a few more problems than it resolves.

Burney is the legal practice support coordinator at Thompson Hine in Cleveland, Ohio.

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