I've been testing a lot of different mail apps for iOS during the years, but I always keeps coming back to the default Apple Mail app because of small (or big) things I'm not liking with all these third party mail apps.
It's one of the best I've tried and I kept using it for a longer time than most of them. But there was some annoying things with it that made me finally switch back again.
For example the formatting sometimes of some html emails made the text way too small to read. They look perfectly fine in Apple mail, but not in Boxer.
And the exchange account requires a 4 digit pin in the Boxer app itself, not only on the phone as with Apple mail…
These are some small things that annoys me so I went back to Apple mail again, and it already feels better. And to be honest, I don't care that it doesn't have push support for Gmail, and only check for new mail every 15 minutes. It's not so stressful that way when I get around 600 emails everyday, but still have inbox zero every day.