We have our own internal VoIP system in which our employees are using to communicate to each other, each VoIP station has an extension number assigned for each employee.

We would like to use Active Directory to add the extension number to our local Active Directory so it can appear on the directory searches and use DirSync so the extension attribute can appear on Outlook and Lync users business cards.

Is it possible do to this? and if yes, how?

We have:

  • A Windows 2012 R2 domain.
  • An Office 365 E3 subscription
  • DirSync one-way replication (no ADFS)



This is a list of useful attributes available on user objects in Active Directory.

You're going to want to populate the TelephoneNumber attribute. DirSync or Azure AD Sync will synchronize this to the GAL in your Office 365 tenant.

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