Apple’s Mail app on the iOS includes a couple handy gestures that let you flag messages, set them as read, or toss them in the trash. You can customize iOS mail gestures according to your habits.
Swipe left to right across a message to mark it as read or unread. Swiping from right to left works slightly differently. A long swipe to the left deletes the email, but swipe a little more slowly to see options such as being able to flag the email to read later.
You can change the way the gestures work in the Settings app -> Mail, Contacts, Calendars -> Swipe Options. Diagrams show the currently assigned actions. Only the actions in the positions shown in blue are changeable – “Flag” and “Mark as Read” by default.
If you tap on Swipe Right, you can change it to either flag the email or file it in the Archive mailbox. If you’re left-handed you might want to change the Swipe Left gesture to “Mark as Read” so that the default actions are reversed.