Why am I forced to set up Microsoft Authenticator in Microsoft 365?

Hello , Welcome to MS Q&A

Even if you've already added a phone number to your Microsoft 365 account, Microsoft may still require you to set up the Microsoft Authenticator app due to:

1. Security Defaults or Registration Campaigns

• Security Defaults: If enabled, these enforce strong MFA registration, and Microsoft prioritizes app-based methods like Microsoft Authenticator over SMS or voice.
• Registration Campaigns: These are enabled by default in many tenants and prompt users to register the Authenticator app, even if other methods like SMS are already configured .

2. Microsoft's Security Strategy

Microsoft is actively deprecating SMS and voice call MFA as primary methods because:

• SMS is vulnerable to SIM swapping and phishing.
• Authenticator apps support phishing-resistant MFA (especially with number matching and location context).
• Microsoft has stated that Authenticator is the preferred method for MFA in Microsoft 365 environments

How to Avoid Being Forced to Use Authenticator

If you're an admin and want to allow users to use SMS instead:

Disable Security Defaults:

• Go to Microsoft Entra ID > Properties > Manage Security Defaults
  • Set to "No"
  Disable Registration Campaigns:

  - Go to **Microsoft Entra ID > Protection > Authentication Methods > Registration Campaign**
  
     - Set **State = Disabled1**
  
     **Configure Authentication Methods**:
  
        - Go to **Microsoft Entra ID > Protection > Authentication Methods**
  
           - Enable **SMS** and **disable Microsoft Authenticator** for specific groups if needed
  

⚠️ Note: These options require Microsoft Entra ID P1 or P2 licensing to fully customize

Pls check similar threads as well for ref --> 1. https://learn.microsoft.com/en-us/answers/questions/1527556/sms-authentication-is-prompting-forcing-me-to-set

2. https://learn.microsoft.com/en-us/answers/questions/1662061/authenticator-app-being-forced

Also MS link for ref -->https://learn.microsoft.com/en-us/microsoft-365/business-premium/m365bp-mfa-for-users?view=o365-worldwide

Pls let us know if further ques

Thanks

Deepanshu