Is there a way to protect Apple Mail with a password

Hi everyone,

I need some help in here. Is there a way to set a password for Apple Mail before the application opens. I know that we can set up a password before receiving new emails, but what about existing ones? Anyone can open the Apple Mail application and read all the inbox. Is there a way to protect the application with a password?

Thank you for your help!

Don't allow other users to log in to your account. Set up separate user accounts for each user on the machine without admin access. If they can't log into your account, they can't see any of your home folder data.

This is done in System Preferences / Accounts

My wife doesn't even have access to my user accounts on any of our computers, while I am the admin on all computers in the house and we both have admin status on her machines. I do not however go poking around in her stuff either unless she asks me to fix stuff she's broken.