Ugh! It’s most annoying when you’re in a full screen app and presenting. Suddenly, Mail.app decides to take half the screen and spurts all my inbox for everyone

Ugh! It’s most annoying when you’re in a full screen app and presenting. Suddenly, Mail.app decides to take half the screen and spurts all my inbox for everyone to see. You can’t watch full time videos either due to this annoyance.