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Microsoft is throwing the full weight of Hotmail behind its Sender ID e-mail authentication technology by sidelining incoming mail when it fails to pass a Sender ID check.

The software maker has begun warning Hotmail users with an on-screen alert when the sender of an incoming e-mail cannot be verified using its Sender ID Framework. Mail that fails to pass the test will be placed in a junk mail folder or could even be deleted, according to Craig Spiezle, director of Microsoft's Technology Care and Safety Group.

Spiezle laid out the changes in an interview posted on Microsoft's Web site this week. Microsoft is pushing Sender ID as a system for identifying and thwarting unwanted e-mail. The technology works by verifying that e-mails originate from the domain from which they claim to have been sent. It checks the sending server's address against a registered list of servers that the domain owner has authorized to send e-mail.

Pushing Its Plan

By making all mail received by Hotmail go through the Sender ID check, Microsoft is not only making a strong play for the technology but also pushing ISPs and other businesses to publish their sender policy framework (SPF) records so that their mail does not get quashed. Hotmail reserves the right to delete mail based on antispam and antiphishing heuristics and on the sender's reputation, Spiezle says. He did not say how reputations are assessed.

Organizations should publish their SPF records to "protect their domain and ultimately enhance their brand name," he says.

Microsoft is not the only major technology player promoting an antispam technology. Yahoo has an authentication technology called DomainKeys, and IBM has rolled out a new antispam technology called FairUCE, or Fair use of Unsolicited Commercial E-mail.

Yahoo licenses out DomainKeys, and recently said it is working with Cisco Systems to combine their antispam technologies and create a new authentication system. IBM is promoting its technology with developers, saying it wants to help them build more effective antispam filters.

More information is available on Microsoft's Web site.