While iOS 7’s smart mailboxes and the new message filters in the iOS 10 Mail app are great for finding flagged and unread items in a single folder such as your inbox, they’re less useful for those situations where you’ve archived a flagged message or filed it away in another folder. Fortunately, the iOS Mail app has a pretty robust search feature borrowed from its bigger brother on macOS, including the ability to search for message status in addition to message content.
Scrolling up to the top of your message list in any mailbox reveals the search field, and if you tap on this you’ll immediately see predefined “Suggested Searches” for unread messages, flagged messages, messages from VIPs, and messages with attachments. Tapping on any one of these immediately initiates a search for messages matching that specific criterion, and if “All Mailboxes” is selected at the top of the screen, the search will go through not only the currently selected folder, but every folder in that particular account to ferret out those messages. You can even combine these searches by typing in the other terms you want to use — for example, tap on “Flagged Messages” to start a search for all flagged messages, and then type in “Attachments” and tap on “Messages with Attachments” at the bottom of the “Suggested Searches” list and your results will be filtered to include only those messages that are flagged and have one or more attachments.
There are also a number of other special search terms that can be used in this field, such as “Today” or “Yesterday” or “Last Week” to find messages from only those time frames — simply start typing in the appropriate word or phrase and then pick the option from the “Suggested Searches” to add them to the list of search criteria. Other date terms can be used as well, such as entering a month or weekday to bring up specific date ranges.