Mail for iOS: You can add custom folders to the Mailboxes sidebar

In Mail’s top-level Mailboxes sidebar, you can enable a number of smart mailboxes and add your own folders for quick access. Some of the pre-built folders are pretty handy, like Attachments, Thread Notifications, and All Archive.

At the bottom of the panel is an Add Mailbox button. Tap that and you can browse your account(s), select one or more folders, tap Done, and rearrange your custom folders among all the built-in options. It’s a simple way to bend Mail to better fit your needs.