Text message verification code

Question

How to fix my cell phone number being blocked from receiving verification codes?

Answer 1

Microsoft may temporarily block a phone number from receiving verification codes if it detects unusual or excessive activity, or if the number is flagged with a bad reputation. To fix this and regain the ability to receive codes, follow these steps in order:

1. Stop repeated attempts

• Avoid repeatedly requesting codes to the same or alternate numbers/emails. Excessive or repetitive requests can cause or extend a block.

2. Wait out temporary blocks

• Many blocks are temporary and automatically clear.
• Wait at least 24 hours without further attempts. If the issue persists, wait longer (up to about a week) before trying again.

3. Check that the number is valid and supported

• Make sure the number is a mobile phone number, not a VOIP number. VOIP numbers cannot be used for Microsoft verification codes.
• Confirm the correct country/region code is selected wherever the number is entered.
• Ensure the phone can receive SMS or calls from international/United States-based numbers, as required in some flows.

4. Fix issues on the phone/device side

• Ensure the phone is turned on and has signal/service.
• Confirm that SMS, RCS, or other text messaging services are active on the device.
• Check that texts or calls from unknown or blocked numbers are not being filtered or blocked.
• Clear out a full SMS inbox or troubleshoot any malfunctioning messaging app.

5. Try another verification method (if available)

• Use an alternate method already configured on the account, such as:
  • Alternate email address
  • Microsoft Authenticator app or verification code
  • Voice call instead of SMS, or SMS instead of voice
• In sign-in flows, choose Other verification options or Try another method when offered.

6. Verify and correct security info

• Have an admin (for work/school accounts) or use the account’s security page to confirm that the correct phone number is registered.
• For Microsoft Entra ID (work/school):
  • An admin should open the user in Microsoft Entra ID and verify the authentication phone numbers and that Block sign in is not enabled.

7. If the number is reputation-blocked (work/school with Entra MFA)

• In cases like error 399287 (“bad reputation” on the phone number for SMS), the resolution is for Microsoft to reset MFA/clear the block on the backend.
• An admin should open a support case with Microsoft (for Entra ID / Microsoft 365) and provide the affected user and phone number details so the data team can remove the bad-reputation flag.

8. Escalate to Microsoft support if nothing works

• If waiting, using a different network/device, and switching methods do not resolve the issue, and especially if the number appears to be blocked globally (no codes from Microsoft at all), contact Microsoft support for the relevant service (Microsoft account or Microsoft 365/Entra) and reference that the phone number appears to be blocked for SMS/voice verification.

Following these steps typically resolves blocked-number issues, either by automatically clearing the temporary block or by having an admin/support engineer remove the block on the Microsoft side.

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References:

• Troubleshoot Microsoft verification code issues
• Common problems with two-step verification for a work or school account
• You don't receive a text or voice call that contains the verification code for Microsoft Entra multifactor authentication
• Authentication methods in Microsoft Entra ID - Voice call
• Troubleshoot issues when you sign up for a new account in the Azure portal
• Azure has blocked myphone number for SMS verification due to a “bad reputation” flag - Microsoft Q&A