Hotmail Pushing Sender ID

As the next step in implementing its Sender ID antispam technology, Microsoft has modified Hotmail so users will see a warning on all messages from unregistered domains. The move could reduce the amount of spam faced by Hotmail users, and eventually spur wider adoption of Sender ID (or supporting technology), making it more difficult for spammers to conduct their business. For now, however, lack of universal support for Sender ID could result in needless warnings, diluting their usefulness.

Not Universally Supported

Sender ID is designed to stop spoofing, a tactic often used by spammers in which the sender forges header information on an e-mail message to hide its true origin. Sender ID works by requiring the owners of mail servers to register the IP addresses of their e-mail servers as Sender Policy Framework (SPF) records in the Internet Domain Name System (DNS, which is used to resolve domain and computer names to the IP addresses needed to route data to its destinations). Then, a mail service provider can check incoming messages against the SPF records to determine if the headers are forged.