Exchange Unified Messaging (UM) provides voice mail services for Voice-over-IP (VoIP) systems. Exchange answers the incoming call, records the messages, and places the message inside the user’s mailbox. This article covers how to configure a secondary dial plan for a user’s mailbox.

What is a secondary dial plan?

While researching a different issue, I came across the topic of assigning mailboxes a Secondary Dial Plan in Exchange Unified Messaging. While I had been studying and researching quite a bit on UM, I had never come across this topic.

According to Microsoft documentation, assigning a user to a secondary dial plan is useful when using an integrated Lync/Skype for Business Exchange UM dial plan. In this type of plan, the user’s extension is the Lync endpoint or SIP address and not a telephone number. If the user requires more extension numbers, then Microsoft recommends not adding a secondary extension on the primary Lync dial plan but adding a secondary dial plan with the telephone extension.

This was actually a lifesaver in the integration of our Lync/Exchange UM dial plan alongside our telephone extension dial plan integrated with Cisco. This allowed us to put the user’s primary dial plan as Lync and the telephone extension dial plan as the one integrated with Cisco. With this configuration, users could use the integrated voice mail options inside the Lync client and also have an IP-based Cisco phone on their desk with both working pretty smoothly.

Configuring Exchange Unified Messaging secondary dial plan

Unfortunately, Microsoft’s documentation really doesn’t tell you how to set a user up with a secondary dial plan. It took a bit of digging, and I found a comment on a different blog site on how to accomplish this. Here are the steps.

First, enable a user on a dial plan based in the US (note, these are not Lync-integrated dial plans, I just threw these together in my lab to demonstrate this):

Run the Get-UMMailbox command to view the current list of extensions for the mailbox:

Also, run the Get-Mailbox and view the EmailAddresses field to see that the user has an EUM address associated with their account from the USDialPlan.

To set the secondary dial plan, you actually don’t use any of the Set-UMMailbox commands but instead use the Set-Mailbox command along with -SecondaryAddress and the -SecondaryDialPlan. Here we are enabling the mailbox on the UKDialPlan:

Run the Get-UMMailbox and Get-Mailbox commands again and see that the user has another extension on the UM Mailbox with each extension showing its assigned dial plan. Also, view the EmailAddresses field on the mailbox itself:

Pretty straightforward to set up but unfortunately the documentation doesn’t list how to set it (not that I could find).

Related: Check out more Exchange content here!

Microsoft TechNet Secondary Dial Plans

Using Exchange Unified Messaging Secondary Dial Plans with Lync and Cisco Communications Manager (the blog where I first read about this and found the comment on how to set it)