Reader Arnie Goldstein asks the question that every iOS user has had flit through their mind at one time or another:
Is there a way, on my iPhone, to delete all the email messages on it without having to tap Edit, tap each and every message on it, and then delete all those I have clicked?
First let me cut some of our commenters off at the pass. Yes, you could send feedback to Apple, but believe me, this feedback has been sent countless times and so far, nothing. I expect it hasn't been implemented because Apple is concerned that Apple Geniuses will be ripped limb from limb when the unwary accidentally wipe their devices of email.
Regardless, attempting to delete hundreds of messages using the currently available methods--tapping Edit, tapping the gray circle next to each message, and then tapping Delete/Archive or swiping across each message and tapping Delete--is the kind of thing that should be reserved for an unpleasant afterlife.
So, if Apple won't provide a solution and you're unwilling to risk a repetitive stress injury, where do you turn? To your computer.
Fire up your email client and clean out the messages you don't want. This could be tedious too--though not as tedious as it would be on your iPhone. If you have an IMAP account such as a Gmail account, you can go to that account via your web browser and archive any messages in the Inbox. If you have a POP account, archive your Inbox (you do this in Apple's Mail by right-clicking on a mailbox and choosing Export Mailbox) so that you have a backup of it. You could then delete all the messages you don't want, but because I'm the careful sort, I'd instead create a new mailbox on your Mac (click the Plus button in the bottom left corner of the Mail window) and move my wanted-yet-not-on-my-phone messages to this folder.
If you have only an IMAP account, that should take care of the problem. When you next check the Inbox for that account, it should be clear of messages. If it isn't or you have a POP account where those messages are likely still sitting on your iPhone, launch Settings, tap Mail, Contacts, Calendars; select your email account; scroll to the bottom of the screen; and tap Delete Account. Once that operation is complete, recreate the account using the usual methods in the Mail, Contacts, Calendars screen. The recreated account should now be clean.