Unable to Verify Identity for Microsoft 365 Login – Error 399287

Question

Unable to Verify Identity for Microsoft 365 Login – Error 399287

Nikola Skopljak 25

Dear Microsoft Support Team,

I'm trying to sign into the Microsoft 365 portal. I can sign in to my Microsoft account, but I'm prompted to verify my identity via SMS. However, I receive the following error message:

“Sorry, we’re having trouble verifying your account. Please try again.”

Error Code: 399287

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 as it is a business account. It would be great if you could unblock the MFA to the account.

I am using another email to post this question since i am not able to access my business account. You can contact me on this email.

Thank you for your kind support

Best Regards,

Shubham Sharma 17,940 Reputation points Microsoft External Staff Moderator

2026-04-21T15:50:44.38+00:00

Hello Nikola Skopljak

Welcome to Microsoft Q&A Platform.

I understand you're experiencing issues logging into your Azure account due to MFA. Based on error code 399287, it appears your multi-factor authentication method is blocked because the phone number has a bad reputation.

Could you please send the requested details via private message so we can further assist?

Thanks

Answer accepted by question author

Shubham Sharma 17,940 Microsoft External Staff Moderator

Nikola Skopljak

Thank you for your patience

Thank you for sharing your details via private message.

I’ve reached out to the engineering team regarding the MFA issue on your account. They have now unblocked it from the backend and cleared the bad reputation associated with it. You should be able to log in to the Azure Portal without any issues.

Please try signing in and verify if you can complete SMS authentication successfully. Let me know if you encounter any problems.

As a best practice, I recommend registering the Microsoft Authenticator method for your account instead of relying on SMS. SMS and voice call authentication methods are more vulnerable to IRSF attacks (telephony fraud) and are generally less secure.

For better practice, I recommend registering with Microsoft Authenticator method to your account instead of SMS method as these SMS/Voice telecom auth methods are susceptible to IRSF attacks telephony fraud.

If the resolution was helpful, kindly take a moment to accept the answer and upvote it 👍 to make it helpful to the community.

Thank you for contacting Microsoft Q&A!

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Your answer

Shubham Sharma 17,940 Reputation points Microsoft External Staff Moderator

2026-04-21T15:50:44.38+00:00

Hello Nikola Skopljak

Welcome to Microsoft Q&A Platform.

I understand you're experiencing issues logging into your Azure account due to MFA. Based on error code 399287, it appears your multi-factor authentication method is blocked because the phone number has a bad reputation.

Could you please send the requested details via private message so we can further assist?

Thanks

Answer 1

Error 399287 indicates that the phone number used for SMS verification has been blocked for multifactor authentication (MFA), often due to a “bad reputation” or other security-related flags on the number. In this situation, self-service options (retrying SMS, password reset, or alternative sign-in) typically do not resolve the issue.

For a business (work) account where sign-in is blocked by MFA and there is no working alternative method, this must be handled by Microsoft support, specifically the Microsoft Data Protection team, who can reset or clear the MFA configuration on the account/tenant.

Use one of these supported paths:

If there is another admin in the tenant
Ask that admin to open a support request from the Microsoft 365 admin center so Microsoft can investigate and reset MFA as needed.
If this is the only admin account in the organization
In this case, the Microsoft Data Protection team must verify identity and help regain access:
- Call Microsoft support using the country-specific number listed under Customer service phone numbers - Microsoft Support.
- When the automated system asks for the problem type, answer along the lines of:
  - Problem: Authenticator / sign-in verification
  - Product: Office 365 for business
  - Account type: Company account
  - Are you an administrator?: Yes
  - Are there any other administrators?: No
- Request that a service request be opened and routed to the Data Protection team to reset or unblock MFA for the affected tenant/account.
If direct support access is not available (no admin portal access, no existing support contract)
As described in the referenced guidance, it is possible to:
- Create a temporary new Microsoft 365 trial tenant.
- Sign in as the new tenant’s admin and go to Support → Help & support in the Microsoft 365 admin center.
- Open a support ticket clearly stating that access is needed to a different, existing Microsoft 365 tenant where the admin account is locked by MFA (Error 399287 on SMS).
- Provide:
  - The admin sign-in name of the locked tenant.
  - The tenant’s domain name.
  - The exact error (including Error Code 399287 and the SMS verification failure).
  - Confirmation that this is the only admin account for that tenant.
- After the issue is resolved, cancel the trial subscription for the temporary tenant to avoid charges.

Once Microsoft support/Data Protection has verified identity, they can reset or clear the MFA configuration for the affected account so that sign-in can proceed and new MFA methods can be configured.

Self-service steps (retrying SMS, changing numbers, or password reset) are not sufficient when the number is flagged with bad reputation and Error 399287 is returned; direct Microsoft support involvement is required.

References: