The secret question is the memorable question you create for security purposes during account/email setup or when you first log in to My Account.
The only time you'll need to supply the answer to your secret question is when you are trying to log in and have forgotten your password. This assures us that you are the person that you say you are. It enables you to log in and reset your password online.
To set a secret question, sign in to manage your account settings.
For information on performing a password reset, please see Resetting your Business Email account password.