While you’re probably already familiar with the Spotlight search feature in iOS 7—simply swipe down from anywhere on the home screen to find it—if you’re often trying to track down specific Mail items, you there are some advanced features you may find useful.
Firstly, keep in mind that if you’re searching from the home screen, iOS will only search the from, to, and subject fields of emails that are already on your device. To perform a more advanced search you’ll need to go into the Mail app and then swipe down to reveal the Search field. Entering a search from here will not only perform a full search on your message content, but also extend the search to messages stored on the mail server that have not yet been downloaded to your device. From here, you can also use keywords similar to those found in the Mac Mail app: for example, a search for “Flagged December 2013” will reveal all messages received in December that you have marked with a flag. Other keywords you can use include VIP, FROM, TO, and various “smart” date formats such as yesterday or last week.
One caveat, however: While iOS Spotlight itself understands these keywords, your mail server may not; once the search continues on the server side, chances are that you’ll simply get literal results for these keywords. Still, this can be a pretty handy way to quickly filter through the mail that is already stored on your device.