Configure the number of incoming calls on a Mailbox server in Exchange Server

Applies to: Exchange Server 2013, Exchange Server 2016

You can configure the number of incoming concurrent connections that a Mailbox server that's running the Microsoft Exchange Unified Messaging service will accept. This includes all incoming calls including Outlook Voice Access, call answering, auto attendants, and fax calls. When you increase the number of concurrent connections on a Mailbox server, more system resources are required than if you decrease the number of concurrent calls. Decreasing the number of concurrent calls is especially important on slower computers on which Unified Messaging services are installed. The range for the number of concurrent voice calls is 0 to 200. The default setting is 100.

For additional tasks related to Unified Messaging and Mailbox servers, see UM services procedures.

What do you need to know before you begin?

  • Estimated time to complete: Less than 1 minute.

  • You need to be assigned permissions before you can perform this procedure or procedures. To see what permissions you need, see the "Mailbox server (UM service)" entry in the Unified Messaging permissions topic.

  • Verify that you've correctly installed the Client Access and Mailbox servers.

  • For information about keyboard shortcuts that may apply to the procedures in this topic, see Keyboard shortcuts in the Exchange admin center.


Having problems? Ask for help in the Exchange forums. Visit the forums at Exchange Server.

Use the EAC to configure the number of incoming calls on a Mailbox server

  1. In the EAC, navigate to Servers > Servers.

  2. In the list view, select the Exchange server you want to modify, and then click Edit Edit icon..

  3. On the Exchange Server page, click Unified Messaging.

  4. Under UM Service settings, under Maximum number of calls allowed, enter a number from 0 to 200, and click Save.

Use the Shell to configure the number of incoming calls on a Mailbox server

This example sets the number of incoming voice, Outlook Voice Access, and fax calls that can be accepted by a Mailbox server named MyMailboxServer1 to 50.

Set-UMService -Identity MyMailboxServer1 -MaxCallsAllowed 50