I got similar it felt... like... how do you think you can compete with us, we're the best.... it's a tough space, you shouldn't even try and get out... when Microsoft's actually looks like it could be a slack killer - a lot more functionality because of everything combined, heck if I was a CEO of my own company I'd probably ditch gmail and get the whole outlook business essentials package for everything and move to microsoft's cloud instead of google's.
This whole idea, from writing the letter to publishing it as a full page ad in the paper, seems bizarre and misguided.