In this section:

Exchange Online UM Connectivity via Skype for Business Server On-Premises

Ribbon SBC Edge Portfolio platforms may be deployed in support of legacy PBX ↔ Exchange Online Unified Messaging (UM) communication for voicemail retrieval and deposit.

Exchange Online UM Legacy PBX Network Topology


Exchange Online UM integration is supported by the SBC Edge Portfolio via the Skype for Business (SfB) Server On-Premises.

  • The SBC does not directly communicate with the Exchange Online UM platform; the SBC communicates with the Exchange Online UM via the Skype for Business Server deployed on-premises. 
  • The SBC can forward a call from the legacy PBX to the Exchange Online UM (via the SfB Server) for voicemail (VM) deposit when required.
  • The Legacy PBX or Skype for Business Server is responsible for determining when a call it is handling needs to be forwarded to Exchange UM for voicemail deposit.

The SBC Edge Portfolio product configuration does not require any special Exchange Online UM configuration to support VM deposit or retrieval services.

  • The SBC Edge Portfolio should be configured for legacy PBX interworking without regard for Exchange Online UM VM deposit or retrieval. VM related calls to/from the legacy PBX are treated as any other calls originating from/terminating to the legacy PBX.
  • The SBC Edge Portfolio should be configured for Skype for Business Server on-premises interworking without regard for Exchange Online UM VM deposit or retrieval. VM related calls to/from the Skype for Business Server are treated as any other calls originating from/terminating to the Skype for Business Server.

Please refer to Skype Related Best Practices for SBC Edge Portfolio configuration guidelines. 

Skype for Business Server On-Premises Required for Voicemail Support

In the past, Microsoft allowed qualified SBCs to interact directly with Exchange Online UM (i.e., no Skype for Business Server On-Premises was required for VM services to/from a legacy PBX). Microsoft announced this topology would no longer be supported as of April 2019. As a result, Ribbon does not recommend the SBC deployment without the presence of the Skype for Business Server. For details, refer to Microsoft's announcement: Discontinue Support for Session Border Controllers in Exchange Online Unified Message.


Message Waiting Indicator Forwarding

Ribbon SBC Edge Portfolio platforms may be deployed in support of legacy PBX ↔ Exchange Online Unified Messaging (UM) communication for Message Waiting Indicator (MWI) related services.

Message Waiting Indicator Notification Topology


Exchange Online UM-generated Message Waiting Indications (MWI) is supported by the SBC Edge Portfolio via the Skype for Business Online Phone System.

  • The SBC does not directly communicate with the Exchange Online UM platform; rather the SBC receives an MWI from the Exchange Online UM via the Skype for Business Server deployed on-premises.
  • The SBC forwards the MWI to the legacy PBX when received.
  • The Legacy PBX is responsible for lighting the MWI indicator on the relevant subtended phone client.
  • The SBC forwards the MWI clearing indication (when received from the SfB Server) to the legacy PBX when the VM has been read; the legacy PBX is responsible for clearing the MWI indicator on the relevant subtended phone client.

The SBC Edge Portfolio product requires special configuration to support VM-related MWI services.


The Message Waiting Indicator feature (including a license fee) is planned for availability early 2019, in advance of the Microsoft April 2019 discontinuance of direct SBC interaction with Exchange Online UM. When available, Ribbon will update this page with details surrounding the specific SBC provisioning to enable the forwarding of MWI-related indications from Exchange Online UM to legacy PBXs.