Prevent Mail pop up automatically when there's a new email I'm using macOS Mojave. Apparently I've changed a setting - but can't figure out which one - that forces Mail to automatically pop up in the active desktop when there's new email. 

For instance, I'm in a desktop with Safari maximized, I receive an email and the Mail app automatically splits the screen and shows the new email.

This happens even when I'm connected to a projector and in a meeting. considering I've even turned on the Do Not Disturb mode when mirroring TV and projectors, it's super strange.

Could you please help me find this option to prevent Mail pop up when there's a new email?
IF you go to Notifications > Mail you should be able to change the Mail Alert Style to "None" to avoid mail alerts altogether.

Source: https://discussions.apple.com/thread/4306641