scubacuda points out this CNET story, writing "In addition to beefing up its storage (100MB -> 250MB), Yahoo! Mail has implemented Domain Keys to find spam. The idea is simple: give email providers a way to verify the domain and integrity of the messages sent. Sendmail, Inc. has released an open source implementation of the Yahoo! DomainKeys specification for testing on the Internet and is actively seeking participants and feedback for its Pilot Program. Yahoo! has submitted the DomainKeys framework as an Internet Draft, titled 'draft-delany-domainkeys-base-01.txt,' for publication with the IETF (Internet Engineering Task Force). The patent license agreement can be found here."