> Mind you, a program with “hidden” windows open takes up more CPU/memory than a program without any windows open I can’t speak to Mail, but in general a Mac a

> Mind you, a program with “hidden” windows open takes up more CPU/memory than a program without any windows open I can’t speak to Mail, but in general a Mac app with no visible windows may actually take zero CPU, because (if it’s written to allow for it) the OS may kill the process entirely.