I can’t delete one email from my account using Apple 11.1

This error occurs sometimes when something has happened to the email if it was deleted by a different device or something similar like that. What things have you tried? Have you tried force closing the app (swipe up from the bottom of the screen and keep swiping past when the dock bar shows up, or double tap the home button, and then swipe the mail app off the top of the screen.)? If it is a webmail service (Google, Yahoo, MSN, etc.) try going to the website and removing it there.