You can instantly mark all email as read with just three taps in Mail for iOS. This is a time saver when you want to skip those marketing or unimportant emails.
Inside Mail app, goto “All Inboxes” or any of the inbox that has multiple unread emails. Tap on the “Edit” button on top right corner to enter the edit mode. And then tap on the “Mark All” button on the left corner of bottom toolbar.
On the popup menu, select “Mark as Read”. That’s it. All the emails in the inbox are now marked read.