AD User Attributes

Checks that phone numbers on enabled Active Directory users are in international E.164 format: a plus sign, the country code and the number, with no spaces or punctuation, such as +14255550100. By default it checks telephoneNumber and mobile; the Attributes parameter can add otherTelephone, otherMobile, homePhone and facsimileTelephoneNumber.

Teams Phone, click-to-call, MFA phone registration and mobile device enrolment read these numbers once they are synced to Microsoft Entra ID, and they only dial reliably when the number is in E.164. A trailing extension such as ;ext=123 or x123 is allowed by default (AllowExtension).

Remediation action

1. Rewrite each number listed below as + country code and number, for example (425) 555-0100 becomes +14255550100.
2. In Active Directory Users and Computers, change the number on the General tab (Telephone number) or the Telephones tab (Mobile, Fax, Home), or use PowerShell: Set-ADUser -Identity <sAMAccountName> -OfficePhone '+14255550100' -MobilePhone '+14255550101'.
3. If your organisation writes numbers with spaces (+1 425 555 0100), set AllowSpaces to $true for this test. For a different rule, set PhonePattern to your own regular expression.

Related links

• Set-ADUser
• Telephone-Number attribute (Active Directory schema)
• E.164 numbering (ITU-T)

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