A plugin for Outlook 2013/2016 and above that prevents accidental shutdown.
I just wrote this plugin to prevent accidental shutdown of Outlook.
You can download the latest version of the plugin directly at here. If you are not comfortable with the security of the compiled plugin, you can download the source code and compile it yourself using Visual Studio 2015 or later.
When you click directly to close, Outlook will automatically restart in the background by default in a minimal way, without worrying about actually shutting down.
If you really want to close Outlook, you can completely close Outlook by holding down the Shift+Close button.