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The creators of the newest version of the Mailblocks Web-based antispam e-mail service are hoping to take the challenge out of its challenge/response technology: The company has unveiled an update featuring improved sender verification that should help cut down the number of challenges the service issues.

Mailblocks' challenge/response technology works by quarantining inbound e-mail messages in a pending folder and then sending an e-mail "challenge" message to the sender. Legitimate senders go to a Web page where they retype a number to verify that they're a real person (computer-generated spam mailers can't complete the task).

Verified messages move into the Mailbocks user's in-box, and the address is added to their master list; nonverified mail stays in the pending folder for up to 14 days before it disappears. Subsequent messages from an approved address go directly to the in-box unchallenged. (Mailbocks users can also add e-mail addresses directly to their master list.)

Less Challenging

The biggest problem with the early version of Mailblocks' technology was that every user had their own master list of verified senders. That meant that even if the service verified you as a real sender on the list for one Mailblocks user, it had to do so again when you sent a message to another Mailblocks user.

The latest version of the challenge/response feature, by aggregating the valid responses from all Mailblocks users, reduces the likelihood that Mailblocks will rechallenge senders, says Phil Goldman, Mailblocks' chief executive officer.

"We figured out this: If you send mail to me at Mailblocks, get challenged, and respond, we know you're a human being," he says.

Senders who complete a successful challenge/response exchange for a single Mailblocks user will not be challenged again if they send e-mail to another Mailblocks user, provided they don't begin spamming users, Goldman says.

Spamlike activity will not be judged simply by the volume of e-mail messages sent out, or the number of recipients for a message, Goldman says. Instead, the company will look at the number of new Mailblocks recipients addressed by the sender, he says.

Because Mailblocks is an e-mail service with a rapidly growing user base, the "do not challenge" list will quickly grow with Mailblocks e-mail traffic volume, something desktop antispam software can't offer, Goldman says.

"You never get challenged, but [we] still eliminate all the spam. It's the best of both worlds," he says.

E-Mail Made Easy

Mailblocks offers users a Web based e-mail interface and 12MB of e-mail storage space for $10 a year, Goldman says. Hotmail charges $20 a year for 10MB of storage.

The Mailblocks service lets users aggregate e-mail from up to ten different accounts, including Hotmail, America Online, and Yahoo. You can view messages through Mailblocks' Web-based interface or download them to e-mail clients such as Microsoft Outlook, Goldman says.

While Mailblocks will work with desktop clients, the company has worked hard to make its Web version work as well and as fast as any program, Goldman says. So, for example, when you compose a message you do so not in a new Web page but in a separate Java window. This arrangement lets you navigate between the message and the rest of your Mailblocks account. If you were to try that with Yahoo, on the other hand, you would have to click the Back button in your browser--and thereby lose your in-progress message.

Mailblocks also includes features that let you receive automated e-mail messages that you wish to receive. You can set up and use "tracker" e-mail addresses, tied to your main Mailblocks address, with online services such as newsletters, mailing lists, and online shopping accounts. The tracker addresses allow such services' legitimate automated messages to get through without challenge. The feature also eases concerns--raised with other attempts to institute challenge/response technology on a wide scale--that Internet newsgroup administrators would be bombarded with challenge messages stuck in endless "mail loops," Goldman says.

Bright Future?

Despite being a newcomer to a well-established market, Mailblocks is pressing the right button with its focus on stopping spam and enhancing usability, according to Michael Gartenberg, research director with Jupiter Research.

"Research shows that a large number of Internet mail users use Web-based e-mail, and their number one complaint is spam. Mailblocks has an innovative approach to that problem," he says.

The service will also be attractive for Internet users weary of churning through e-mail accounts whenever they change Internet service providers, he says.

"It's similar to when Google entered the market," Gartenberg says. "People said, 'Is there room for another search engine so late in the game?' And the answer was yes. Even in an established market, there's always room for people to do better."

While declining to give exact numbers, Goldman says Mailblocks is still small compared with its competitors.

Still, the company's user base has expanded quickly since the service launched in March, and it is growing at a rate of around 5 percent a week, Goldman says.

While not challenging the dominance of the big ISPs in the short term, Mailblocks may eventually force them to get serious about stopping spam and to spiff up their user interfaces, making them more akin to desktop applications than sluggish Web pages, Gartenberg says.