Multi factor authentication to text message service

Question

We have an Office 365 account used by IT - for security reasons it's the only global admin account and it's hardened with MFA. However, there is a catch-22 of when one has to authenticate - where does the authentication go for a shared device? A single mobile phone is not practical. Neither is an office phone an option as no everyone has access to that phone (different offices/locations). Plus you don't have the option to send to an email :-(

So somebody had the bright idea of setting up a cloud text message service where the code would be forwarded to a shared email account. Should work well.

Except... we've tried a trial with Textanywhere and whilst we can send text messages to the account from our own mobiles, whenever we ask MFA to send a text code, it never arrives.

Is the problem here with Microsoft or the text messaging service? I haven't asked TextAnywhere yet but suspect that they are blocking Microsoft text messages? It is the free trial account at the moment.

Alternatively is anyone else using a cloud text messaging service for this purpose?

Answer 1

Hello Rob Nicholson (Helios),

Thank you for reply, we understand your concern but to check from our end, we need detail information about your Authentication method and detail information about your MFA settings. Could you please kindly provide us detail information , so we can check further.

However after some more research found that, Microsoft does not guarantee consistent SMS or Voice-based Multi-Factor Authentication prompt delivery by the same number. In the interest of our users, Microsoft may add or remove Short codes at any time as we make route adjustments to improve SMS deliverability. Microsoft does not support short codes for countries/regions besides the United States and Canada. You can check detail information on Phone authentication method article : https://docs.microsoft.com/en-us/azure/active-directory/authentication/concept-authentication-methods#phone-options

Thanks and regards,

Ankita Vaidya

Answer 2

Hello Rob Nicholson (Helios),

We haven't heard back from you. If you need any help from our end, we request you to provide us the above requested information at your convenience.

Thanks and regards,

Ankita Vaidya

Answer 3

Hi Ankita - I'm fully aware of the various options but to distil my question down into simpler terms:

Why isn't the text message received when using a text messaging service?

For the specific service I'm trying to use (TextAnywhere) it could be that you don't get a fixed telephone number. So my supplemental question would be:

Has anyone successfully set-up a shared text messaging service to receive MFA authentication codes and if so, which one?

Answer 4

Hello Rob Nicholson (Helios),

Thanks for your post in Microsoft Community. Generally for MFA, depends on user’s Authentication method and alternate contact method, user will receive his/her verification code. In Additional security verification set up, we have three options for “How should we contact you : Authentication phone, Office phone and Mobile app”, Which option had you selected? Could you please kindly provide us the step by step information, so we can check at our end and update you accordingly.

Here we would like to share some Article for MFA for your reference:

• Set up 2-step verification for Office 365: https://support.office.com/en-us/article/set-up-2-step-verification-for-office-365-ace1d096-61e5-449b-a875-58eb3d74de14?ui=en-US&rs=en-US&ad=US
• Use Microsoft Authenticator with Office 365: https://support.office.com/en-us/article/use-microsoft-authenticator-with-office-365-1412611f-ad8d-43ab-807c-7965e5155411

Thanks and regards,

Ankita Vaidya

Answer 5

Ahh... maybe found the problem with TextAnywhere. I've just sent another test message and the number it was sent from has changed. So maybe with this text provider, you don't get a fixed incoming number.

The search continues...