Mailblocks service simplifies challenge-response

A new e-mail service aims to put an end to unsolicited commercial (“spam”) e-mail by collecting the addresses of legitimate e-mail senders on to a master list that will take the “challenge” out of “challenge-response” for many e-mail users.

Four month-old Mailblocks Inc. on Monday unveiled Challenge/Response 2.0, the latest incarnation of its patented Challenge/Response technology.

Challenge/Response is similar to technology used by other Internet service providers (ISPs), including Earthlink Inc.

Using the technology, Mailblocks quarantines inbound e-mail messages to its accounts, sending an e-mail “challenge” message back to the sender with a request to type a seven-digit number into a box.

The challenge requires the human sender to view a unique number displayed on a Web page and transcribe it, something computer-generated spam mailers can’t do.

Once a valid response is received from the sender, the initial e-mail is retrieved from quarantine and delivered. The sender’s e-mail address is then added to the user’s valid sender list, enabling subsequent messages to be received without challenge.

The latest version of Challenge/Response reduces the likelihood that senders will get challenged by Mailblocks by aggregating the valid responses from all Mailblocks users, according to Phil Goldman, Mailblocks’ CEO.

“We figured out this — if you send mail to me at Mailblocks, get challenged and respond, we know you’re a human being,” he said.

Users who complete a successful challenge-response exchange for a single Mailblocks user will not be challenged again, provided they don’t begin spamming users, Goldman said.

The principle is akin to one credit card companies use with their members, he said.

“So as long as you’re a member in good standing with Visa, you don’t have to call them each time you need to charge something. The catch is, if you start to do something funky with your Visa card, they might block that card and force you to call them. It’s the same thing here. If you start to spam, we’ll start to challenge you again,” he said.

Spam-like activity will not be judged simply by the volume of e-mail messages sent out, or the number of recipients for a message, Goldman said.

Instead, the Los Altos, California, company looks at the number of new Mailblocks recipients addressed by the sender, Goldman said.

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 said.

“You never get challenged, but still eliminate all the spam. It’s the best of both worlds,” he said.

Mailblocks offers users a Web based e-mail interface and 12M bytes of e-mail storage space for $9.95 a year, compared with $19.95 a year for 10M bytes of storage on Hotmail.

Mailblocks is also throwing in two years of membership free, Goldman said.

The service allows users to aggregate e-mail from up to ten different accounts, including Microsoft Corp.’s Hotmail, America Online Inc. (AOL) and Yahoo Inc. messages can be viewed through Mailblocks’ Web-based interface or downloaded to e-mail clients such as Microsoft Outlook, Goldman said.

While the challenge-response technology weeds out spam e-mail, Mailblocks also allows users to set up so-called “tracker” e-mail addresses, tied to their main Mailblocks address, that can be used with online services such as newsletters, mailing lists and online shopping accounts.

The tracker addresses allow legitimate automated messages generated by those services to get through without challenge. The feature also addresses 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 said.

Besides the huge advantage of weeding out spam, Mailblocks offers the advantage of fast response times, making it more like a desktop e-mail application than a Web-based service, Goldman said.

Despite being a newcomer to a well-established space, Mailblocks is pressing the right button with its focus on stopping spam and 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 said.

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

“It’s similar to when Google entered the market,” Gartenberg said. “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 said Mailblocks is still small compared to its competitors.

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

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 spiff up their user interfaces, making them more akin to desktop applications than sluggish Web pages, Gartenberg said.