If you use the built in Mail app on your iPhone or iPad and deal with sifting through a lot of email messages, you’ll likely appreciate a small feature that Apple added in iOS 10, which gives you the ability to quickly and easily filter your message listing. A button in the bottom-left corner of the Mail app will toggle on a filtered view that provides quick filtering of messages in the current mailbox. By default, the filter will show you only flagged messages. However, if you tap on the “Filtered by” link that appears in the bottom status bar when the filter is enabled, you can refine the filter with other criteria, including unread messages, messages addressed To or CC’ed directly to your email address (as opposed to those from mailing lists), or only messages with attachments or messages from contacts on your VIP list. Multiple criteria can be combined here as well, so you could include both unread and flagged messages, but only those which include attachments.
Your last used settings are retained and will be used the next time you apply the filter, so you specify whichever criteria you most commonly filter by, and then just toggle the filter on and off with the filter button in the bottom left corner. While this feature is similar to the Smart Mailboxes introduced in iOS 7, it has the advantage of being customizable on the fly, and working in any folder that you happen to be viewing, not just the Inbox. In addition, your filter settings and on/off status are saved individually for each folder, so you can have different defaults set up for different folders, and you can even choose to leave your filter on within specific folders.