Error Code: 399287

Question

I am head of support in my company [Moderator note: personal info removed] and I have used my personal mobile number for MFA in several administration office 365 accounts for customers in order to handle their setups and renewals. Suddenly I have been blocked out in and when I try to login I get “Sorry, we’re having trouble verifying your account. Please try again.” and Error Code: 399287. I looked it up and I found that according to microsoft my number has a bad reputation.

Please help me, I have been locked out from customer accounts and its creating a big problem, both form me and my customers.

What should I do to solve this problem?

Answer 1

Hi @STYLIANOS PAGKALOS,

Thank you for reaching out and taking the time to explain the situation in detail.

Being suddenly blocked from signing in - especially when you manage multiple Microsoft 365 customer tenants - can be highly disruptive and understandably concerning. The error message and Error Code 399287 you’ve shared are key details, and the context about using a single mobile number for MFA across several administrative accounts is especially relevant here.

Error Code 399287 typically indicates that SMS or voice verification is being blocked by Microsoft’s Phone Reputation or risk protection controls. When this occurs, the sign‑in process cannot complete even if the correct username and password are entered. Unfortunately, when SMS is the only configured authentication method, there is no self‑service option available to clear or reset the phone reputation status independently. Resolution usually requires either assistance from another administrator or direct intervention from Microsoft Support.

 

Here are recommended next steps:

1/ Contact an IT administrator within your organization

If there is another IT or Global Administrator in your organization, please reach out to them and request a reset of your MFA authentication methods. They can follow the guidance outlined in Manage user authentication methods for Microsoft Entra multi-factor authentication to reset your MFA configuration.

Once your MFA has been reset, the next sign‑in will prompt you to set up authentication again from the beginning, including registering the Microsoft Authenticator app by scanning a new QR code. This is the most effective way to restore access if another admin is available.

 

2/ Contact Microsoft Data Protection Support by phone

If no other administrator is available to assist, 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 to contact our global customer service by phone to request a reset of your authentication method here: Customer service phone numbers.

 

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 a sample message to help you navigate the IVR system 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're 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 worried about?

You: Authenticator.

IVR: What products do you use?

You: Office 365 for business.

Verification: Education or business account?

You: For companies.

IVR: Are you an admin?

You: Yes.

IVR: Are there other admins 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.

 

While direct intervention isn’t possible from this forum, guiding you to the correct, specialized support path is the most effective assistance that can be provided here. Hopefully, these steps help you regain access as quickly as possible and reduce the impact on both you and your customers.

As other users may also search for information in this community, your vote can greatly help those with similar questions quickly find the most relevant resources.

Thank you for your kindness and I wish you a wonderful day ahead.

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Answer 2

How can I open a ticket in non admin account

Answer 3

Error code 399287 in this scenario indicates that SMS-based verification using the phone number has effectively been blocked due to “bad reputation” or unusual activity on that number. Since that number is used for MFA across many customer admin accounts, it is being treated as risky and is no longer accepted for verification.

There is no self-service way to clear this reputation or unblock the number. The resolution requires direct Microsoft support intervention for the affected tenant(s), similar to other MFA/lockout cases where SMS verification is no longer working.

To move forward:

1. For each affected customer tenant, open a support ticket from an account that can still sign in (for example, another admin or a partner account). Clearly state:
   • Error code 399287
   • That SMS MFA to the shared admin phone number has stopped working due to bad reputation
   • That this number is used for multiple customer admin accounts and that access is blocked.
2. Ask support to:
   • Escalate to the Microsoft 365 Data Protection or identity support team, as appropriate, to remove the block or assist with resetting MFA for the impacted admin accounts.
   • Help reconfigure MFA to use more reliable methods (for example, Microsoft Authenticator app or per-tenant admin phone numbers) instead of a single shared SMS number.
3. If a tenant is completely locked out (no admin can sign in because all rely on that number), treat it as a tenant lockout/MFA issue and request escalation in the ticket so the Data Protection team can help restore admin access.

Once Microsoft support has intervened, they can help restore access and adjust MFA so that future administration does not depend on a single SMS number with a high-risk reputation.

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References:

• Troubleshoot Microsoft verification code issues
• Common problems with two-step verification for a work or school account
• 399287 - Microsoft Q&A Unable to Verify Identity for Azure Login – Error 399287
• Severity A Situation - Locked out of global admin account (MFA) - business down - Microsoft Q&A