Apache have written an open letter to the IETF regarding the Sender ID proposal. Sender ID is a technology designed to reduce spam on the internet. Although well designed and a technology that could do a serious amount towards reducing spam, the proposal is tied up with patent problems. Who's the prime culprit? Your favourite vendor, Microsoft.
"The current Microsoft Royalty-Free Sender ID Patent License Agreement terms are a barrier to any ASF project which wants to implement Sender ID. We believe the current license is generally incompatible with open source, contrary to the practice of open Internet standards, and specifically incompatible with the Apache License 2.0. Therefore, we will not implement or deploy Sender ID under the current license terms."
The decision lays out the position for not just Apache, but SpamAssassin and JAMES. SpamAssassin is a major tool for server administrators attempting to stop spam, and is deployed worldwide. The Apache decision highlights the view of the majority of the Open Source community. Although Microsoft are offering the technology "royalty free", the way they have constructed the license makes it impossible to fuse Sender ID with open source / license technologies; Lawrence Rosen writes that the "Microsoft Sender ID patent license continues the convenient fiction that there are "End Users" (S1.5) who receive limited rights. That is unacceptable in open source licenses."
Baring in mind that most of the web services are based around open standards, it looks like Sender ID is destined for a slow death. That is, unless Microsoft reconsider the situation.
Screenshot: How Sender ID works