I hate the New Mail. I liked Mail Classic, and am very sorry it has disappeared. I am really surprised that New Mail was released (much less FORCED on us), with all the bugs.
1) One can no longer add an e-dress (with the NAME) to the contact list after sending a message to a new person. It will add, but only as the e-dress itself. No name. So you have to search for the e-dress in the contact list and then add the name manually. Or add the whole thing manually. Who thought that was a better idea???? When I send to a dozen new people at one time, this is incomprehensibly useless. It was fine - Why did you change it?!
2) The keyboard commands for "next email" and "Previous email" are idiotic. Why not Control + (up arrow)? Who can remember whether Control+[,] is up or down?
3) The keyboard command for "save as unread" is also unintuitive. SHIFT+K? are you kidding me?
4) Many more things, but this is enough ranting for now.
Oh yes, AND, I have been hearing from my clients that they are not even receiving my messages sometimes. This never happened before July 2013, when we were forced to migrate to New Mail. This is the most unacceptable thing of all.