Error Code: 399287 MFA via SMS not working - BadReputation

Question

Error Code: 399287 MFA via SMS not working - BadReputation

Kristian Bentsen Kjærgård (KBK) 65

We are experiencing an issue with MFA via SMS in our tenant and have been for the past few months or so. When attempting to use SMS for MFA, the authentication fails with the following error:

{"Success":false,"ResultValue":"BadReputation","Message":"BadReputation","AuthMethodId":"OneWaySMS","ErrCode":399287,"Retry":false,"FlowToken":"Removed","SessionId":"","CorrelationId":"<pii removed>","Timestamp":"2026-06-09T12:45:13Z","Entropy":0,"ReselectUIOption":0,"ContinuationToken":null,"MobileAppAuthDetails":null}

Request: Unblock the tenant from the Azure Phone Fraud Protection system, making us able to use SMS MFA again.

I'm able to provide email address, phone number, tenant id, country and country code if requested via a private message. We are unable to contact the Data Protection team, as when we get through the AI assiatants, the phone is hung up from their side for some reason.

Thank you in advance.

Best regards,

Kristian

Shubham Sharma 17,930 Reputation points Microsoft External Staff Moderator

2026-06-15T06:12:50.36+00:00

**Kristian Bentsen Kjærgård (KBK)**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

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Your answer

Shubham Sharma 17,930 Reputation points Microsoft External Staff Moderator

2026-06-15T06:12:50.36+00:00

**Kristian Bentsen Kjærgård (KBK)**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

Kristian Bentsen Kjærgård (KBK)

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.

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