One of the things I learned early on in internet marketing is that when I am writing a mass email, I think about it going to one person. One person. One person is going to read it. So I write to one person. The email just feels different when you write to one person. It might be a representative person (like a persona) or it might be to a real person on your list.
Then simply send that email to your mass list. The odds of each person feeling like that email was written just to them, goes up exponentially, in my opinion.