Microsoft 365 admin center - Unable to login by verifying using SMS

Question

Good morning!

We're unable to log into our Microsoft 365 tenant's Admin Center because verifying using SMS is not working. The system claims the account is not verified but doesn't allow any other options (error Code 399287).

I found in a few other post this can be solved by the engineering team, so I'm tagging the person from Microsoft that was able to get this fixed: @Raja Pothuraju , could you do the same for me?

Kind regards,

Johan

Answer 1

Hello @Johan Verbelen,

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.

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