The war on spam continues on a number of fronts. In addition to improving spam-detection and spam-blocking technologies, vendors are pursuing authentication and trademark protection of domain names to fight spam.Authentication, while not an anti-spam tool per se, does determine whether the mail server used by the sender of a message is an approved sender. Although there are a number of good authentication schemes that have been proposed, I feel that Sender ID (the merger of Sender Policy Framework, or SPF, and Microsoft\u2019s Caller ID) will ultimately become the leading standard for e-mail authentication, although likely not the only one.Most recently, Cloudmark and IronPort Systems announced their support for Sender ID. Earlier, ClickZ advised organizations that market through e-mail to obtain an SPF record and FrontBridge Technologies has announced support for SPF and Sender ID. Last month, Microsoft\u2019s Hotmail service announced it would begin verifying incoming e-mail for SPF records in the fourth quarter.Some time back, I proposed using trademark law (as have others) to protect domains from being spoofed, or at least giving domain owners some recourse to prosecute spammers who use a domain name in an unauthorized manner. Because domain spoofing (the practice of using a domain to send spam fraudulently) can be so injurious to the reputation of a domain owner, there should be some way that damaged parties can fight back.To help establish service mark (the equivalent of a trademark) protection for domain names, the Institute for Spam and Internet Public Policy (ISIPP) last week announced it has started a service to help business owners register their Internet domains for protection under U.S. trademark law. For a fee of $225, ISIPP will prepare the application for the U.S. Patent and Trademark Office, have the application reviewed by an attorney, conduct a conflict search to determine whether or not a domain has already been granted service mark status and electronically file the application. Although the ISIPP service does not include the filing fee of $335, the service does all the legwork to register the domain.All of this reflects the continued, broad-based efforts to reduce the amount of spam affecting individuals and enterprises using processes and techniques that will supplement technology-based approaches.