We have no immediate plans to implement that.  We will wait a bit to see some level of general adoption, specifically popular email clients that support it or customers requesting it.  I've seen a lot of 'proposed standards' disappear over time so I'm not inclined to jump on new ones until there is a clear movement behind them, and there is something about that standard which really bothers me (but I may be missing the point as I've only had a quick read of it)... 

 

Anyway, we will keep an eye on it and certainly take note of any requests.