Safari mail app
how to turn off mail app permanently or delete it
MacBook Pro 13″, macOS 10.14
Question marked as
Some Apple apps such as Safari re installed as part of the computer's operating system and can not be removed as they are write protected. I am not sure, but I think that Mail is in that category. I suggest that you simply remove the Mail icon from the Dock by dragging it to the Trash and then not using it. It can reside in your Applications folder unused.