There seems to be quite a lot of confusion when it comes to voicemail services in Microsoft’s offerings, whether it be on-premise servers or in the Office 365 suite. Which is understandable, given there are a plethora of scenarios and they each have their own technical dependencies. In this article, I will be giving a high-level overview of these voicemail solutions that are native with the Skype for Business (Skype4B) and Exchange product lines.

Note that Skype4B/Lync always requires a secondary product that provides voicemail services and e-mail messaging deposit. There are other 3rd Party voicemail solutions available that I will NOT be covering in this article (example: AVST).  It is also important to note that Exchange Unified Messaging (UM) is able to provide voicemail services to Skype4B/Lync and to traditional PBX’s.


  • 10-4-2016: Table has been updated to include new scenario (#2 below) with the delivery of Cloud PBX Azure Voicemail to Exchange Server UM On-Premises
  • 7-18-2017: Table has been updated to include the End of Life of Exchange Online UM & IP-PBX via SBC (Scenario #6)

Here is a table of the possible scenarios and the appropriate Voicemail solution.


As you can see, your organization may have users that fall into a single scenario or even all of them! It can get a little daunting if you have a large mix of users and a support ticket is submitted with “My voicemail doesn’t work”.

Scenario 1

  • Telephony Solution – Skype for Business Online Cloud PBX
    • This includes the following Cloud PBX solutions:
      • PSTN Calling
      • On-Premises PSTN Connectivity (Hybrid Voice)
      • Cloud Connector Edition (CCE)
  • Exchange Mailbox Solution – Exchange Online
  • Voicemail Solution – Cloud PBX Voicemail – hosted in Azure and comes bundled with the Cloud PBX user license.
  • Description – An Exchange Online Mailbox is required only for the actual email deposit of the voicemail recording – this is NOT leveraging the Exchange Online Unified Messaging service.
  • Technical Resources


Scenario 2

  • Telephony Solution – Skype for Business Online Cloud PBX.
    • This includes the following Cloud PBX solutions:
      • PSTN Calling
      • On-Premises PSTN Connectivity (Hybrid Voice)
      • Cloud Connector Edition (CCE)
  • Exchange Mailbox Solution – On-Premises Exchange Server
  • Voicemail Solution – On-Premises Exchange Server Unified Messaging
  • Description – All services are on-prem. Skype4B/Lync communicates with Exchange UM for voicemail. Also, Exchange Server provides e-mail deposit. OAuth between Skype4B Online and Exchange Server on-prem is the key mechanism with this scenario.
  • Technical Resources


Scenario 3


Scenario 4


Scenario 5


Scenario 6

IMPORTANT NOTICE:  Exchange Online Unified Messaging for 3rd-party PBX connections via Session Border Controller (SBC) will be discontinued as of July 2018.

Please see the official announcement:

  • Telephony Solution – Traditional PBX (Avaya, Cisco, Nortel, etc.)
  • Exchange Mailbox Location – Exchange Online
  • Voicemail Solution – Exchange Online UM
  • Description – requires a Voice Gateway/SBC to establish a secure SIP trunk from the local PBX to Exchange Online. You may already have an IP-PBX that is capable to be configured to connect to securely to the cloud, check the TechNet articles that follow to verify. NOTE – the SBC/Gateway is the key component that is securing the communications over the internet to Office 365.
  • Technical Resources


Hopefully this helps when you are considering to adopt a new technology, troubleshooting a user’s issue, or an Exchange guru working on mailbox migrations.