Heh. Did you try Airmail? That's the only one that I liked.

The only reason I'm not using it today is that I was using the beta, and at one point they did a lot of frequent bugfix releases, and each new release started to require that you set up all your settings (mail accounts etc.) from scratch. I got tired of it and abandoned the thing.

I'm sure it's better now, I just haven't felt like going through all the steps again yet. Airmail does plaintext email, too.