Error code 399287

Question

User account: [Moderator note: personal info removed]@hmspartner.onmicrosoft.com getting error code 399287 on phone number [Moderator note: personal info removed]. This is a private account, there is no other option to login and no IT admin to help with resetting MFA options. We are not able to get in touch with Microsoft support and need help of removing bad reputation.

Answer 1

Hi @Khuram Azeem,

I’m very happy to share some guidance and support you here.

To start with, I’d like to gently clarify that based on the account you provided, the .onmicrosoft.com domain indicates this is a business account, as it’s linked to a Microsoft business subscription. That said, it’s quite common for these accounts to be used by a single individual for personal purposes rather than within a larger organization. To better understand your setup, could you please confirm whether you personally purchased the subscription, set up this account yourself, and are the only person using it?

If that’s the case, then you would be considered the administrator of this tenant. In situations like this, where the only admin account is locked out due to MFA and needs to regain access. Your case will need to be reviewed directly by the Microsoft Data Protection team, as they are the only team with the appropriate tools and verification processes to help restore access to administrator accounts.

Please contact Microsoft Support directly using the regional phone numbers listed on Customer service phone numbers - Microsoft Support    

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.   

(Please use this script to navigate through the automated prompts effectively and reach a live support agent. Once connected, you can then explain your specific situation in detail.) 

If you have any updates or if there’s anything that feels unclear, please feel free to leave a comment directly under this post. That’s the best way for me to receive notifications and make sure I can follow up with you as quickly as possible.

Thank you again for your patience.

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Answer 2

Error code 399287 indicates that the phone number used for SMS verification has been blocked due to a “bad reputation” flag in Microsoft Entra multifactor authentication. This cannot be cleared through self-service; it must be handled by Microsoft support/data protection.

Based on similar resolved cases:

1. If this is a work/school (business) account and there is at least one other admin in the tenant:
   • Another global admin must sign in to the Microsoft 365 admin center and open a support ticket with Microsoft.
   • In the ticket, they should clearly state that SMS verification for the specified phone number is failing with error 399287 and request MFA reset / removal of the bad reputation flag for that number.
2. If this is a work/school account and there is only one admin (the locked-out user):
   • Contact Microsoft support by phone and ask to be connected to the Microsoft Data Protection team to regain access to the administrator account and reset MFA.
   • Use the country-specific number from Customer service phone numbers - Microsoft Support and follow the automated prompts similar to:
     • Problem: “Authenticator”
     • Product: “Office 365 for business”
     • Account type: “For companies”
     • Are there any other administrators: “No”
     • Request: “Service request”
   • The Data Protection team has tools and processes to verify identity and reset MFA when the only admin is locked out.
3. If direct phone support is hard to reach and there is absolutely no other way to open a ticket from the affected tenant:
   • Create a temporary new Microsoft 365 trial tenant.
   • From that new tenant’s admin center, open a support request and clearly state that the request is for a different, existing tenant where the admin is locked out due to error 399287 on SMS MFA, and provide:
     • Admin UPN of the locked tenant
     • Tenant domain
     • Error code 399287 and description (bad reputation on phone number)
   • Work with support until MFA is reset and access is restored, then cancel the trial subscription.

Self-service options (changing password, trying again later, or switching networks) will not remove the bad reputation flag in this scenario; only Microsoft support/Data Protection can clear it and reset MFA.

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References:

• Troubleshoot Microsoft verification code issues
• Microsoft account has been locked
• "Sorry, but we're having trouble signing you in" when a user signs in to Microsoft 365, Azure, or Intune
• MFA admin account no longer works - Microsoft Q&A
• Azure has blocked myphone number for SMS verification due to a “bad reputation” flag - Microsoft Q&A
• Error Code: 399287 - 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 speak with a real person and it seems impossible. - Microsoft Q&A
• Common problems with two-step verification for a work or school account