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Problem with Azure b2c sending 2fa mobile authentication sms to Chechia nunbers

Andreas Mavromichalis 1 Reputation point
2025-07-25T12:05:34.4566667+00:00

This is similar to our request with ID: 2411****0001506

When a Czech mobile number (+420 **PII removed**90) is used for 2fa on the azure b2c built in login flow the user does not receive an sms and gets the error (The phone number you provided is unreachable)

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Microsoft Security | Microsoft Entra | Microsoft Entra External ID

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  1. Raja Pothuraju 29,245 Reputation points Microsoft External Staff Moderator
    2025-07-28T13:11:55.0633333+00:00

    Hello Andreas Mavromichalis,

    Based on the error message you received it appears that was SMS authentication for country code +420 is blocked because it is not in allow listed countries.

    We addressed this by collaborating with our internal team, who have now unblocked your SMS or Voice MFA Region Block for +420 country code.

    You can check and confirm whether you were able to register SMS in the tenant which was blocked.

    If you request to block a region due to suspected fraud, you can refer this document Mitigate fraudulent sign-ups.

    Hope this helps. Let us know if you have any queries. Happy to assist you further.

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