How do I search email on my iPad Air 2?

If in iOS Mail, if you are not seeing the search box at the top of the left hand column, simply make sure you are at the top of your most recent email in the list to reveal the Search box.

Then, input your search term and a list below the search box will start to form where you can tap on to target your search or simply hit the return key to enter your search trems

You can limit the search of your emails to either all mail boxes or current mail box by swiping down on the email list to reveal two thin boxes that read "All Mailboxes" or "Current Mailbox"

Good Luck!