AOL, Yahoo rolling out sender authentication

ISPs (Internet service providers) America Online (AOL) and Yahoo plan to begin using technology to verify the source of e-mail messages in coming months, as both companies step up efforts to stop unsolicited commercial, or "spam," e-mail, according to information provided by the companies.

In September, AOL will verify the source of incoming e-mail using a component of Microsoft's Sender ID authentication architecture. Yahoo will use its DomainKeys authentication technology to sign all e-mail coming out of the company's mail servers by the end of 2004, according to spokesmen for the companies. The decisions are part of an industry-wide push to thwart spam and online scams known as "phishing attacks," by improving the ability of ISPs and e-mail providers to verify the source of e-mail messages, according to interviews with executives from e-mail technology companies.

AOL will screen mail using Sender Policy Framework (SPF) technology beginning in September, said Nicholas Graham, an AOL spokesman, in an e-mail statement. SPF is part of Sender ID, a proposed technology standard backed by Microsoft for verifying an e-mail message's source.

Sender ID combines two previous standards: the Microsoft-developed "Caller ID," and SPF, developed by Meng Weng Wong. The combined standard was submitted to the Internet Engineering Task Force (IETF) in June for consideration. If adopted, Sender ID could provide a way to close loopholes in the current system for sending and receiving e-mail that allow senders -- including spammers -- to fake, or "spoof," a message's origin.

AOL, based in Dulles, Virginia, has been testing SPF since January, publishing SPF records that identify AOL's outgoing e-mail servers in the DNS (domain name system), which translates numeric IP (Internet Protocol) addresses into readable Internet domain names. However, the ISP has not yet used SPF to screen incoming e-mail.

AOL will begin checking whether the purported responsible address, or PRA, of the e-mail server sending mail matches one of the servers listed in the SPF record for that Internet domain. Tens of thousands of e-mail domains have published SPF records. AOL will use SPF to help it determine which messages are legitimate, rather than using it as a criteria to reject e-mail, Graham said.

That approach is similar to one Microsoft announced in July, when it said it will begin matching by Oct. 1 the source of inbound e-mail to the IP addresses of e-mail servers listed in that sending domain's SPF record. Messages that fail the check will not be rejected, but will be further scrutinized and filtered, said Craig Spiezle, director of Microsoft's Safety Technology and Strategy Group.

Yahoo is looking to put its thumbprint on outbound, rather than inbound, messages. The Sunnyvale, California, company will roll out its DomainKeys technology by the end of 2004, digitally signing all e-mail messages sent from its servers, said Miles Libbey, antispam product manager at Yahoo.

DomainKeys use PKI (Public Key Infrastructure) technology to create a unique signature for each e-mail message based on the content of the e-mail message. When e-mail servers receive DomainKeys signed messages, they use a public encryption key published by the company in the DNS record for the sending domain and the contents of the message to verify the source of the e-mail, he said.

The movements by Microsoft, AOL and Yahoo are a sign of the increased urgency with which e-mail and Internet service providers are treating the spam problem.

"The world of e-mail is in a lot of hurt. It's in trouble and there's a sense of urgency we haven't seen," said Greg Olson, chairman and co-founder of e-mail technology company Sendmail Inc.

Pushing technologies like Sender ID and DomainKeys into service even before their official adoption as standards by the IETF or other governing bodies is a way to safely work out problems the technologies may cause when widely deployed, Libbey said.

"All these solutions are reasonably early in the life cycle. ...There's a lot of interoperability testing that has to happen. Implementing DomainKeys on Yahoo will give us real-world data on how it works," he said.

"It's an iterative process," said Microsoft's Spiezle. "We have to try something. The spammers are outsmarting us and the more we delay, the more time they have to figure out what to do."

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