Checklist: Connect a Traditional PBX to Exchange Online UM

Applies to: Office 365 for enterprises

Exchange Online Unified Messaging (UM) provides voice mail services to Exchange Online and Microsoft Office 365 for enterprises users. UM doesn’t provide a dial tone, voice call switching, or numbering service. You must provide the dial tone to UM from a suitable telephony solution.

The following diagram shows how to provide a dial tone by connecting your PBX to Exchange Online UM.

Connecting a Traditional PBX to Exchange Online UM


  1. Install and configure a VoIP gateway   Select, install, and configure a VoIP gateway compatible with your PBX and Exchange Online UM. To learn more about the VoIP gateways that have been tested and work with traditional PBXs and Exchange UM, see Telephony Advisor for Exchange 2010 and the VoIP gateway/PBX configuration notes in PBX Configuration Notes Tested by Microsoft or IP Gateway Vendor Partners for Exchange 2010 Unified Messaging.
    Note   For more information about how to configure your PBX, see Understanding PBX and IP PBX Configurations and Understand Secure Cloud UM Infrastructures.
  2. Set up your VoIP gateway and session border controller (SBC)   Refer to the manufacturer's instructions for your VoIP gateway and SBC hardware, which, in some cases, may be different parts of the same device and do the following:
    1. Install and configure the hardware.
    2. Attach the VoIP gateway and SBC to your internal IP network.
    3. Assign a public address to your SBC, for example, Test to verify that external DNS clients can resolve this address.
    4. Configure your PBX and VoIP gateway to work together according to the relevant configuration note. This configuration is the same as if what you would use if Exchange UM were running on- your own premises.
    5. Configure your SBC to communicate with the VoIP gateway. For more information about the SBCs that have been tested with Exchange Online UM, see Session Border Controllers Tested with Exchange Online UM.
  3. Create a UM dial plan to connect to Exchange Online UM   In Exchange Online UM, create a telex UM dial plan and a UM IP gateway to communicate with your SBC. Here's how: Create a New UM Dial Plan and Configure a UM Dial Plan.
  4. Configure the SBC to connect to Exchange Online UM   Refer to the manufacturer's instructions and configure the SBC so traffic from your IP PBX is forwarded to and from to Exchange Online UM, using the forwarding address for the UM IP gateway that you just created. For more information about setting up Office 365 UM to work with SBCs , see Configuration Checklist: Configure Office 365 Unified Messaging to Work with a Session Border Controller, Forward Calls from Your Physical Telephone Device to UM, and Session Border Controllers Tested with Exchange Online UM.
  5. Get a Certificate for Exchange UM Online   You must get a certificate for your SBC to establish trust between your SBC and Exchange Online UM for secure communication over the public Internet.
  6. Verify that UM is Working. If you can’t verify that UM is working, troubleshoot your configuration by using the UM Troubleshooting Tool.