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Error 399287 - MFA error send sms

Support GR 40 Reputation points
2026-05-12T09:38:37.5966667+00:00

Dear Microsoft,

I am admin and I have an account with 11 licenses Microsoft 365 Basic Business and the system ask me to enable MFA, however when I try to send SMS I receive the following Error Code: 399287

Request Id: 22c334dc-1c3b-4c14-bcdb-4f8882201b00

Correlation Id: 8909db44-ddde-461a-856b-bfbb25e27106

Timestamp: 2026-05-12T09:05:23Z

As a result I cannot logon to my account and I have just one time to connect without MFA enabled. If I have the opportunity I need to login into security info and define Microsoft authenticator as 2 level authentication.

How I can reset MFA since Microsoft send me this error and I can't receive SMS?

Could you pls support me?

Microsoft Security | Microsoft Entra | Microsoft Entra ID

Answer accepted by question author

VEMULA SRISAI 13,135 Reputation points Microsoft External Staff Moderator
2026-05-12T11:52:53.06+00:00

Support GR I have reached out to the engineering team to unblock MFA for your account. They have now unblocked it from the backend and removed the bad reputation on it. You should be able to log in to the Azure Portal without any issues.

Please try logging in and check if you can complete SMS authentication without any errors. Let me know if you encounter any issues.

I hope this information is helpful. Please feel free to reach out if you have any further questions.

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment". Thanks

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AI answer

2026-05-12T09:39:01.5133333+00:00

Error 399287 indicates that the phone number used for SMS verification has been blocked for Azure MFA due to a “bad reputation” or similar issue at the SMS layer. In this state, SMS verification will not work and MFA must be reset by Microsoft support so that another method (such as Microsoft Authenticator) can be configured.

Because the account is effectively locked out and there is only one admin, this must be handled by Microsoft support / Data Protection teams, not by self-service.

Recommended actions:

  1. Open a support ticket with Microsoft
    • As the Microsoft 365 Business Basic tenant admin, open a support case through the Microsoft 365 admin center (or via your existing support channel).
    • Clearly state that:
      • SMS-based MFA fails with Error 399287.
      • The admin account is locked out because SMS is the only MFA method.
      • You need MFA reset / re-registration and removal of the “bad reputation” block on the phone number.
    • In similar cases, the Microsoft Data Protection team has reset MFA and cleared the block so that users could sign in again and configure new methods.
  2. Ask support to reset MFA for the affected admin account
    • Request that support:
      • Reset MFA for the admin account (clear existing methods and require re-register).
      • Remove or override the bad-reputation flag on the phone number if applicable.
    • This is the same pattern used in the referenced cases where “Azure has blocked my phone number for SMS verification due to a ‘bad reputation’ flag” and “Unable to verify identity for Azure login – Error 399287”; in both, the Data Protection team reset MFA and resolved the issue.
  3. After MFA is reset by Microsoft
    • Once support confirms MFA has been reset and access restored, sign in and immediately:
      • Go to the Security info page for the admin account.
      • Add Microsoft Authenticator as the primary MFA method.
      • Optionally add a second backup method (another phone or email, if allowed by policy) to avoid future lockouts.
  4. If there are other admins in the tenant (for future reference)
    • A global admin can require re-registration of MFA for a user so they can configure methods again, as described in the guidance for managing user authentication options.
    • However, when the only global admin is locked out, escalation to Microsoft support/Data Protection is required, as in the “Severity A – Locked out of global admin account (MFA)” scenario.

Until Microsoft support resets MFA and/or clears the phone number block, SMS verification will continue to fail with 399287 and self-service changes to MFA methods will not be possible.

References:

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