What are swipe options and what are their functions?
In Mail on iOS, you can swipe messages left or right to perform quick actions on that message, such as archiving or marking as read. The action performed when swiping in a certain direction is configured in Settings → Mail (Contacts & Calendars) → Swipe Options.
To quickly delete an email, swipe left or right and hold. This would allow all three swipe functions (schedule, archive and delete) to be simultaneously available.