Telephone System Integration with UM

To successfully adopt Unified Messaging (UM), it is crucial to have a comprehensive knowledge of basic telephony terms and elements. With this understanding, one can seamlessly integrate UM into an existing Exchange organization. The fundamental concepts and parts that must be grasped consist of:

– Circuit-switched and packet-switched networks
– Private Branch eXchange (PBX)
– IP PBX
– Voice over Internet Protocol (VoIP)
– VoIP gateways

Connecting and configuring the mandatory telephony elements form the most intricate steps in successfully establishing UM in any environment, be it on-premises, hybrid, or Microsoft 365. This goes hand in hand with using Microsoft Lync Server and UM. When bringing up a new UM deployment or revamping a legacy voicemail system, one might face several challenges, due to the need for extensive knowledge about VoIP gateways, PBXs, IP PBXs, Microsoft Lync Server, and Unified Messaging.

Upon integrating your telephony network with Unified Messaging, your existing Exchange Server deployment or the UM with Microsoft Lync Server for your organization must be well-analyzed to avoid potential issues. In deploying UM within an Exchange organization, the integration and configuration of either a single or multiple VoIP gateways to connect to the PBXs in your telephony network is necessary, or the same must be done for Session Initiation Protocol (SIP)-enabled PBXs or IP PBXs.

UM leverages the ability of the VoIP gateway to convert Time Division Multiplexing (TDM) or circuit-switched based protocols from a PBX to IP-based protocols. The selection of an appropriate VoIP gateway, IP PBX, SIP-enabled PBX, or SBC is just the initial part of fusing your telephony network with UM. The correct configuration of these devices to harmonize with UM is key to a successful integration.

Unified Messaging and Microsoft Lync Server can provide an all-rounded communication experience, which includes voice messaging, instant messaging, advanced presence, audio/video conferencing, and email integration. Rerouting of voicemail over the PSTN in case Exchange servers aren’t available is handled by the Exchange UM routing component housed in the Lync Server. If the WAN link fails, the Survivable Branch Appliance reroutes unanswered calls over the PSTN to a centrally located Exchange server and fetches voice messages over the PSTN.

For a detailed overview of Microsoft Lync Server, please check Microsoft Lync Server.

Light edits were made in 2025 to improve clarity and relevance.