Audience: IT professionals and administrators

Author: Michael Wilson, Principal Program Manager in Exchange UM


Microsoft Exchange, as Exchange Online, is a key part of the Microsoft Office 365 online services.

Exchange Unified Messaging (UM) is a component of Microsoft Exchange Online, offering:

  • Voice mail in the Inbox
    • Inline playback in Outlook 2007/2010 or Outlook Web App
    • Voice Mail Preview (speech to text) in 7 UM languages (US English, Canadian English, French, Italian, Portuguese, Polish, Spanish)
  • Call Answering Rules
    • Customize greetings, menus by caller, time of day or free/busy status
    • Allow callers to reach you at 1 or 2 unpublished numbers (e.g. mobile phone)
  • Outlook Voice Access
    • Speech or touch tone access to messages, calendar, directory and personal contacts
    • Triage mail, make calls from any phone without needing to look at it or touch it
  • …and much more, including Automated Attendants and Message Waiting Indicator.

Now, Office 365 customers can experience the simplicity and power of UM as part of their subscription.


Here’s what’s needed to use Office 365 UM:

  1. A service plan (Exchange Online Plan 2 or Office 365 Plan E3) that includes licenses to use UM
  2. A telephony/voice solution to provide the “dial tone”. This can be :
    1. Microsoft Lync Server 2010 (with Enterprise Voice), or
    2. An IP PBX that is compatible with UM, or
    3. A PBX and voice-over-IP (VoIP) gateway that is compatible with UM
  3. (Only for customers with PBX/IP PBX) A Session Border Controller that is compatible with UM

Requirement number 2 is much the same for customers that use UM in Office 365 or run it, as part of Exchange 2010, on their own servers. The only difference is that, on the customer’s premises, UM can also be used with Microsoft Office Communications Server (OCS) 2007 and 2007R2.

Lists of PBXs, VoIP gateways, and SBCs that have been tested for compatibility with UM are maintained in the Telephony Advisor for Exchange 2010. It shows the devices for which support is available from Microsoft or a partner. This is not a complete list of all PBXs and gateways that have been used successfully with Exchange UM. Systems integrators may offer advice and support for other configurations as part of service contracts.

Using Microsoft Lync with Office 365 UM


Figure 1 . Office 365 Customer (Fabrikam): Lync with UM Online










Figure 1 shows a simplified view of an Office 365 customer (Fabrikam, Inc.) that is using UM Online with Microsoft Lync for Enterprise Voice.

The Lync servers are operated by Fabrikam and are located on Fabrikam’s premises. All the Exchange servers are in a Microsoft Datacenter.

Communication between Lync servers and Exchange UM takes place over Fabrikam’s Internet connection (labeled Public IP network in the figure).

For reasons of security, Fabrikam must use a Lync Edge Server to act as the proxy and media relay for the voice-over-IP traffic to and from Office 365.

Using PBXs with Office 365 UM



Figure 2 . Office 365 Customers (Contoso and Northwind): PBXs with UM Online










Figure 2 shows a simplified diagram that illustrates two Office 365 customers (Contoso Corporation and Northwind Traders, Inc.) that are using UM Online. These customers are not using Microsoft Lync for Enterprise Voice. They may be using Lync for presence, instant messaging, application sharing and other functions, but this is not shown.

Contoso has a PBX that does not natively support voice-over-IP. They are using a VoIP gateway to convert the signaling and media so that their PBX and Exchange UM can communicate.

Northwind Traders have an IP PBX that supports VoIP communication with Exchange UM, so they do not need a VoIP gateway.

The PBXs and VoIP gateway are operated by Contoso and Northwind, and are located on their premises. All connections to and from the public telephone network are made through the PBXs.

Communication between the VoIP gateway (Contoso) and IP PBX (Northwind) and Exchange UM in the Microsoft Datacenter takes place over the customers’ Internet connections (Public IP network).

For reasons of security, Contoso and Northwind each must use a Session Border Controller (SBC) to act as the proxy and media relay for the voice-over-IP traffic to and from Office 365.


Office 365 Unified Messaging offers “voice mail in the cloud”, and more. It can be used by customers with a wide range of PBXs and IP PBXs, and with Microsoft Lync Server 2010.

For more information about setting up Exchange UM, you can see the following wiki and help articles: