To quit (close) a Mac app normally, choose Quit from the app's menu in the menu bar, or press Command (⌘)-Q. How to get apps off of mac toolbar. If the app doesn't quit, follow these steps to force the app to quit.
How to force an app to quit
Press these three keys together: Option, Command, and Esc (Escape). Or choose Force Quit from the Apple menu in the upper-left corner of your screen. (This is similar to pressing Control-Alt-Delete on a PC.)
Then select the app in the Force Quit window and click Force Quit.
You can even force the Finder to quit, if it stops responding: Select Finder in the Force Quit window, then click Relaunch.
Force Close App Mac
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Force Close Program Mac
To force quit, when you click on the mail app icon you will see your finder bar changes from finder to mail, click the apple icon and find force quit in the menu, select the mail app and tell it to force quit. I think the key combination to force quit is Command+Option+Esc. At the upper-left corner of Mac screen, you will find the 'Apple' icon. Click on that icon. By clicking on it, your system will load a drop-down list. With a number of other available options, select 'Force Quit' from that drop-down menu. Thank you so much!!! Worked on the first try. Spent all day trying every other fix recommended by every other person in the world. I could not even keep mail open long enough to delete any mail. Mail app Inbox kept growing; meanwhile gmail showed 7,000 emails but Mac mail app showed 21,000 emails. It was a disaster. Now it is perfect.
How To Force Close Mail App On Macbook Pro
How to force an app to close on your iPhone, iPad, or iPod touch.