Two-factor authentication provides your mailbox with additional protection by allowing you to access your GMX Account only if you can successfully identify yourself twice using what are known as security factors. The first security factor is your password. If you successfully enter your email and password, you will be prompted for the second security factor. The second security factor is a unique, temporarily valid security code that is generated by an authentication app for each new login.
To log in with two-factor authentication, you will therefore need an authentication app. For an overview of available free and paid apps along with links to additional information, please visit Selection of apps for two-factor authentication.