So, after upgrading to 10.10.3 yesterday I opened mail. When I did, it told me that it was updating the mail database (if I remember correctly). While it was doing that it made mention that there had been several helpful changes/upgrades to the mail application and that I could 'click here' to read about them. I went to click on the link but the update to the database finished up before I could click and I wasn't able to open the link. Since then, I have looked around on line to see what exactly these improvements were but I haven't been able to find anything on it. Did any of you get to read the documentation about the mail changes?