mail won't quit : i tried to put an new email account, did not work out, asking me to put add new account, will not close these 2 windows, and not mail, what can i do, thanks for your help

Do a backup, preferably 2 on 2 separate drives.

Quit Mail. Restart the computer if necessary. If int won't restart, turn the computer off using the power button.

Go to Finder and select your user/home folder. With that Finder window as the front window, either select Finder/View/Show View options or go command - J. When the View options opens, check ’Show Library Folder’. That should make your user library folder visible in your user/home folder. Go to Library/Containers/com.apple.mail. Move the folder com.apple.mail to your desktop. You must move the entire folder, not just the contents.

Restart, re-launch Mail and test. If the problem is solved, recreate any required Mail settings and import any emails you want to save from the folder on the desktop. You can then put the folder in the Trash. If the problem remains, return the folder to where you got it replacing the one that is there.

If that doesn’t solve it repeat the above using Containers/com.apple.MailServiceAgent.

Information learned from Linc Davis. Thanks to leonie for some information contained in this.

Mail crashing

Crashes/quits unexpectedly

Sorry, NOT helpful. The help offered is weak... seems like apple has node how to fix things with el capitan... so many unhappy people who got this... I am not happy either... worst operating system ever

Try command - option/alt - esc to Force Quit Mail. Reopen and test.

C

You might want to consider starting your own post in the El Capitan community. Please provide details of what Mail is doing that is unexpected.

Need help with the question I forgot it

If can't send me and email to do it thank

Thanks Captain Obvious. But forced quit is not working either.