Error Code: 399287

Question

Unable to Verify Identity for Microsoft 365 email login – Error 399287

I can successfully sign in to my WORK Microsoft account, but then, I'm prompted to verify my identity. However, when I do SMS verification, I receive the following error message:

Error Code: 399287

Request Id: [Moderator note: Personally Identifiable Information removed]

Correlation Id: [Moderator note: Personally Identifiable Information removed]

Timestamp: 2026-07-27T15:39:14Z

I'm aware that this is a known problem with SMS, and "bad reputation" for phone number.

And no other options for MFA is offered.

I have already tried alternative login methods and password reset options but have been unable to complete the identity verification process. I would appreciate your assistance in resolving this issue as soon as possible. Please let me know if any additional information is required.

I can send necessary information of my WORK Microsoft account to remove this "bad reputation".

Thank you for your support.

Answer 1

Hi Arny,

I'm sorry to hear that you're unable to complete the identity verification process for your Microsoft 365 work account. I appreciate the detailed information you provided. 

Based on the information shared, it appears that your username and password authentication is successful, but the SMS-based MFA verification is failing with error code 399287, which is commonly associated with Microsoft's phone reputation and fraud protection mechanisms for SMS authentication.  

To help restore access, I recommend the following steps:  

1/ Contact your IT department 

• If you're an end user, please reach out your organization's IT admins and share the guidance provided in the article Manage user authentication methods for Microsoft Entra multifactor authentication. This will help them review and reset your authentication methods, which may restore access to your account. 

• In case you do not know who is your IT admin, kindly refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support   

2/ If you are the only administrator in the tenant 

• If you're the only admin, in this situation, the Microsoft Data Protection Team has tools and processes in place to verify identity and regain access to administrator accounts. You can try reaching out to our Global Customer Service phone to raise a request for resetting your authentication method here: Customer service phone numbers - Microsoft Support. (Work account)

  

Please note that forum moderators do not have access to user account settings and cannot assist with logging in, resetting passwords, or changing access rights. While we do not have access to internal systems or administrative tools required to resolve account-specific or backend-related issues but we’ll continue doing our best to support you within the scope of our responsibilities.      

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.)    

  

IVR: What kind of problem are you concerned about?    

You: SMS verification issue.    

A: What products do you use?    

You: Office 365 for business. 

Verification: Education or company account?    

You: For companies 

IVR: Are you an administrator?     

You: Yes. 

IVR: Are there any other administrators in your organization?     

You: No. 

IVR: Do you need a... Service request?     

You: Yes. I need to create a ticket. Please send me directly to the Data Protection Team. 

Alternative method: Create a new tenant to submit a support ticket 

If you cannot reach a live agent, there is still a workaround, you might consider registering for a new tenant by signing up for a trial subscription and submit your request from there.      

  

To set up a new tenant, please follow these steps below: 

  

Visit Microsoft 365 Business Plans and Pricing | Microsoft 365. This would allow you to create a new tenant following the prompts provided. Once set up, you can access the admin console of the new tenant and submit a support ticket requesting to speak with the Data Protection team on behalf of your previous tenant.       

  

Follow the guided setup process to create a new account for a new tenant.   

  

Once your tenant is created, you should be able to access the support portal and submit your ticket referencing your locked account without further issues 

  

In your ticket description, you'll need to clearly explain that you're trying to regain access to your previous Microsoft 365 tenant and need help from the Data Protection team. Here's a message you can use or adapt:   

  

"Hello, I'm currently unable to access my Microsoft 365 work account. I can successfully sign in with my username and password, but I am unable to complete the required identity verification step because SMS verification fails with Error Code 399287. 

Unfortunately, no alternative authentication methods are available, leaving me unable to complete MFA and access my account. I believe this may be related to a phone reputation or SMS verification issue. 

If I am the only administrator for the tenant, I would appreciate being connected with the appropriate support team to review my case and advise on the available account recovery options. I am available to provide any information required to verify my identity and ownership of the account. 

This issue is urgent, as I rely on Microsoft 365 for my daily work and have been unable to access my services."   

  

Ticket Support: In the Microsoft 365 Admin Center > Support > Help & Support. You can raise support ticket at https://admin.microsoft.com/#/support/requests     

  

Please remember to cancel the trial subscription after your issue is resolved, as this will help you avoid any accidental billing. You may prefer the following resource for detailed instructions: Cancel your Microsoft business subscription in the Microsoft 365 admin center | Microsoft Learn 

  

I hope this helps you regain access to your account quickly. I'm glad to assist and truly hope the information provided has been useful. Please feel free to reach out anytime if you need further assistance.  

If you find my post helpful, kindly consider marking it as the accepted answer. Doing so can assist others in the community who may have similar questions in finding solutions more quickly.  

Thank you for your kindness and contributions to the forum.   

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