Passing along an iOS tip that I frequently find useful though I'm not sure it's even documented. That's the ability to undo the (accidental) deletion of an email. It's particularly helpful with the ability to long-swipe-left on an email to delete it with one touch. Sometimes I find that I've done this to the wrong message and would like to get it back.
Easy. Just shake the phone for "undo" and the last deleted message will pop right back into your inbox. In fact, if you've deleted several you can keep shaking and undelete them one at a time to get back to the one you want.
I'm not sure when this feature was introduced but it's been around since at least iOS 7 and carried forward into the (as of this writing) current iOS 8.1.