When you sign in to Microsoft 365 for the first time, you have to authenticate yourself with another method (SMS on smartphone or mobile app) in addition to entering your OST password. Please have your smartphone ready for the following instructions!
Download the Microsoft Authenticator mobile app from the App Store, Google Play, or the Microsoft Store:
- Open your Microsoft 365 Security Information Settings
- Click on Add method here and select Authenticator app:
- Then follow the instructions on your phone to complete the configuration.
- Now all that remains is to customize the default login method. Click Change and select Microsoft Authenticator - Notification:
The Multi-factor authentication with the "Microsoft Authenticator" mobile app is now set up.
You can find more tips here: How do I set up multi-factor authentication methods?
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Instead of multi-factor authentication with the mobile app Microsoft Authenticator, you can also use multi-factor authentication with SMS.