Ever since I upgraded ios to watever is the newest version, I cannot get the mail app to quit/shut down and my Mac will not shut down or restart. Any help?
Hold CMD+alt+esc keys down to select force quit Mail.
Bootup holding CMD+r, or the Option/alt key to boot from the Restore partition & use Disk Utility from there to Repair the Disk, then Repair Permissions.
Reboot, does Mail still have a problem?
Retrieving data ...