Just a quick note regarding a nice little feature discovery in Apple's stock Mail app in iOS 7 that I haven't seen reported on thus far.
Prior to iOS 7, creating a new message in the stock Mail app would normally default to your 'send from' email address specified in the Settings app. iOS 7 has changed this behavior, for the better.
You see, Mail in iOS 7 is smart enough to over time learn who you're emailing and changes the 'send from' value accordingly to match the recipient's domain. I've included screenshots and the full description right after the break...