The ExUM Routing Application

Exchange UM routing can be configured to route calls to users who are enabled for on-premises Exchange UM, to users who are enabled for hosted Exchange UM, or to a combination of the two.

For example, suppose that Roy’s mailbox and Exchange UM service are homed in an on-premises Exchange deployment.

• The proxy address information from Roy’s user account provides the information that the ExUM Routing application uses to route his calls to an on-premises Exchange UM server.
  
  

Alice’s mailbox and Exchange UM service are located at a hosted Exchange service provider’s data center. Routing for her Exchange UM calls is configured as follows:

• The values set in the msExchUCVoiceMailSettings attribute of Alice’s user account tell the ExUM Routing application to check for routing details in a hosted voice mail policy.
  
  

  Note:
  The value of the msExchUCVoiceMailSettings attribute can be set by either the Exchange service provider or the Lync Server administrator. In the example shown in the preceding diagram, the value (CsHostedVoiceMail=1) was set by the Lync Server administrator to enable hosted voice mail for Alice. For details about this attribute, see Hosted Exchange User Management.

• The hosted voice mail policy that is assigned to Alice’s user account provides routing details:
  
  
  • Destination is the hosted Exchange UM service provider (ls.ExUm.<hostedExchangeServer>.com in this example).
    
    
  • Organizations are identified by the tenant IDs, which are the routing FQDNs for SIP messages for Exchange Server tenants that are located on ls.ExUm.<hostedExchangeServer>.com (corp.contoso.com and corp.litwareinc.com in this example).
    
    For details, see Hosted Voice Mail Policies.
    
    

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Example of mixed deployment Exchange UM routing