E-mail authentication protocols offer a way to protect legitimate messages and address the growing spam crisis. E-mail marketers face many frustrations: phishing, filters, spoofing, blacklists. The image of e-mail as a marketing channel, once so bright, has been obscured by research that suggests as much as 90% of all e-mail messages are spam. This problem could cost marketers as much as $50 billion worldwide in 2005. The CAN-SPAM Act was passed by Congress at the beginning of 2004, and an addendum has been proposed that would lower compliance with opt-out requirements within three rather than the ten days currently in effect. Some business-to-business lobbyists maintain shortening the interval would limit opportunity for smaller media companies that might not be able to afford the technology to process opt-outs more quickly. While the debate over rules continues, e-mail executives are looking to accreditation, authentication, and reputation systems to stem spam's tides. Microsoft Corp. provided Sender ID protection for MSN Hotmail in June 2005, and requires marketers to publish their Sender Policy Framework records. With 200 million global users, Hotmail would appear to have made a bold move in wounding spam seriously if not fatally. Some industry observers see Sender ID as leading the way in a noble fight, since legitimate marketers quickly complying would boost their reputations as well as getting their mail delivered. One critical move is educating advertisers about authentication. Adding a kind of caller identification to e-mail would certainly be welcomed by consumers.