A year ago, it certainly looked like a standards battle was brewing concerning various email sender authentication techniques. While some of the different standards did eventually merge, no real standard came out of it, so Microsoft appears to be doing what it likes to do in those situations and just ram through its own standard as if it was the default.
That's why Microsoft has announced that any email not using their Sender ID system will automatically be put in the junk mail folder. In other words, Microsoft is basically making its email offerings via MSN and Hotmail a lot less useful, since a lot of perfectly legitimate email is probably going to get flagged as junk. [via Techdirt]