Cannot Verify Identity for Login – Error 399287

Question

When I select phone verification for, I am prompted to verify my identity via Authenticator or mobile phone/SMS. I lost access to my Authenticator, but the phone number is still correct.

Clicking verification through phone/SMS immediately fails and returns the following error code.

Error Code: 399287

Request Id: [Moderator note: personal info removed] 

Correlation Id: [Moderator note: personal info removed] 

Timestamp: 2026-03-01T11:22:05Z

I'd be grateful for any help.

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Moderator moved from Microsoft 365 and Office | Access | For business | Windows

Answer 1

Hi @Damian van Dijk, 

Thank you for posting your question in the Microsoft Q&A forum, and I’m really sorry that you’re running into this problem.

I reviewed the details you provided, and the error 399287 is quite specific. In most cases, it means that the phone number you’re trying to use for SMS verification has been flagged with a “bad reputation” in Microsoft’s internal PhoneReputation service. When a number is flagged this way, the system blocks SMS codes from being sent or validated, even if the number is still correct and belongs to you. 

If you are an end user, the next step is to reach out to your organization’s IT administrator and ask them to revoke your existing MFA sessions and force a re‑registration of your authentication methods. They can follow this documentation: Manage authentication methods for Microsoft Entra multifactor authentication - Microsoft Entra ID |…

Once your authentication methods are reset, the next time you sign in, you’ll be guided through the MFA setup process again. Since your phone number is currently being blocked by the reputation system, I strongly recommend that you use Microsoft Authenticator as your primary MFA method during the re‑registration process. It will help you avoid running into this same error again.  

If you’re an administrator, things work a little differently. If there’s someone else with admin rights in your tenant, they can reset your MFA for you. But if you’re the only admin, the only way forward is to contact Microsoft Support by phone.

In this situation, the Microsoft Data Protection team has tools and processes in place to verify identity and regain access to administrator accounts.  

Please note that forum moderators have no control over user accounts, especially when it comes to logging in to your account, resetting your password, changing your access, etc 

Here are some tips and an example of a prompt to help you navigate the IVR more effectively:  

(When you call the support number, you may hear an introduction of about 30 seconds such as "you can visit the link...". You can ignore this introduction and wait until you are presented with the options. Then press "1" as a business email user, and again "1" for technical help.)    

In some regions, the initial interaction may be automated, so here’s a general idea of how the conversation might go to help you prepare:      

What kind of problem are you experiencing?         

Answer: Authenticator         

What products do you use?         

Answer: Office 365 for business         

Is this for an education or company account?         

Answer: For companies         

Are you an administrator?         

Answer: Yes         

Are there any other administrators in your organization?         

Answer: No. I am the only admin in my tenant          

Do you need a... Service request?          

Answer: Yes. I need to create a ticket. Please send me direct to the Data Protection Teams.      

During the phone call, you will need to provide the information associated with your subscription, such as your company name, billing details, phone number, and an alternate email address, etc. This information allows the Data Protection team to verify your identity and securely assist you in regaining access to your administrator account.    

I hope this information helps you take the right steps to regain access to your account. While I’m not able to intervene directly, guiding you to the right support team is the most effective help I can provide here. 

If you have any updates or additional questions, feel free to reply to this thread. I’ll be glad to assist further wherever I can. 

Thank you very much for your understanding.  

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Answer 2

Error 399287 indicates that the phone number used for SMS verification has been blocked by Azure/Microsoft 365 due to a “bad reputation” or similar protection measure. In this state, SMS verification will consistently fail, and self-service options (like retrying SMS or switching back to Authenticator) will not clear the block.

Because access to Authenticator is lost and SMS is blocked, recovery requires intervention from Microsoft support or a tenant administrator with the right tools:

1. If there are other administrators in the organization:
   • Another Global Administrator can reset multifactor authentication methods for the affected account and/or require re-registration of MFA so that new methods (such as a new Authenticator registration or a different phone number) can be configured. See: “Require re-register MFA so that you can configure the MFA methods again.”
2. If this is the only administrator account (single-admin tenant):
   • The Microsoft Data Protection team must be involved to verify identity and restore access.
   • Use the country-specific hotline from Customer service phone numbers - Microsoft Support and follow the automated prompts until a service request is opened with the Data Protection team (for example, answer “Authenticator”, then “Office 365 for business”, confirm it is a company account, and that there are no other admins).
   • Clearly state that:
     • Error 399287 appears when using SMS verification.
     • The Authenticator app is no longer accessible.
     • This is the administrator account for the tenant.
   • The Data Protection team can reset MFA and clear the block so that sign-in and MFA setup can be completed again.
3. If unable to open a ticket from the locked tenant:
   • If the subscription is through a partner/reseller, contact the partner and ask them to open a service request with Microsoft on behalf of the organization.
   • As an alternative, create a temporary trial Microsoft 365 tenant, go to the Microsoft 365 admin center for that trial, and open a support ticket from there, explicitly stating that the problem is with a different, existing tenant where the admin is locked out. Provide the locked-tenant admin UPN, tenant domain, and the error details.

Forum moderators and standard support channels cannot directly remove the “bad reputation” flag or send verification codes; only the Microsoft Data Protection team and/or tenant Global Admins with portal access can reset MFA and restore access.

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References:

• Troubleshoot Microsoft verification code issues
• Common problems with two-step verification for a work or school account
• Authentication methods in Microsoft Entra ID - Voice call
• Error when you try to reset your password in Azure, Office 365, or Intune: We could not verify your account
• Error Code: 399287 - Microsoft Q&A Unable to Verify Identity for Azure Login – Error 399287
• Azure has blocked myphone number for SMS verification due to a “bad reputation” flag - Microsoft Q&A
• I have a Micrsoft business account and I am the admin and the only user registered under this account. I can't log in because i have replaced my phone and the authenticator doesn't work. - Microsoft Q&A
• I need to reset my mfa methods - Microsoft Q&A