Let me read the full e-mail instead of making me scroll from side to side!
I would much rather sacrifice ~visual quality~ for not having to scroll back and forth just to read the full contents of an e-mail. Zoom out doesn't work to do this (it won't let me zoom out to the point where I don't have to scroll side to side).
Dr. T commented
Indeed. I agree with all said by Jackie. This simple ability should be the first thing on the developers's to do list.