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Quick tricks for migrating Exchange UM to Office 365

If you plan to move UM-enabled mailboxes to Office 365 as part of a hybrid implementation, keep it simple to avoid complications.

Exchange Server's Unified Messaging offers value to organizations that have removed reliance on third-party voicemail...

systems and use Exchange's built-in features to provide a single, unified inbox for email and voicemail.

For organizations moving to Office 365, remember that Unified Messaging also needs to be migrated to Exchange Online. The Unified Messaging server role in Exchange only communicates with mailboxes while on-premises; you'll need to configure your phone system to talk to Office 365 to continue using Exchange UM.

Prerequisites for migrating UM-enabled mailboxes

We'll focus on the steps required to set up Lync Server-based telephony systems. Before you attempt to configure your environment or move mailboxes, you'll need to meet a few pre-requisites.

  • Configure your Lync environment with Edge Servers enabled and make sure you've correctly configured federation.
  • Purchase the correct Office 365 licensing. You'll either need the E4 plan or the Exchange Online Plan 2. Some Office 365 versions, including E3, Kiosk plans or Exchange Online Plan 1, don't include this functionality.
  • Implement DirSync and your hybrid Exchange configuration. Correctly license the mailboxes you're migrating with UM.
  • If you have firewall restrictions, make sure these are correctly configured per a normal hybrid configuration. Ensure your Lync Edge servers can send and receive traffic from the Exchange Online data centers.

Configure your Lync phone system

You'll need to configure Lync so it understands where Exchange Online mailboxes are located. The configuration is relatively simple if you're looking to migrate voicemail for end users' mailboxes. Your existing on-premises and cloud configuration can also coexist without end users losing functionality.

First, configure Lync so it has a Hosting Provider, which will be Exchange Online. We'll need to configure a pilot number associated with a Lync contact and then create a Hosted Voicemail policy, which we'll be able to assign to end users. 

Create the new Lync Hosting Provider for Exchange UM
To create a new provider, you'll want to use the New-CsHostingProvider cmdlet and specify the Exchange Online UM proxy fully qualified domain name (FQDN) "exap.um.outlook.com."

New-CsHostingProvider -Identity:'Exchange Online' -Enabled:$True -EnabledSharedAddressSpace:$True -HostsOCSUsers:$False -ProxyFqdn:exap.um.outlook.com -IsLocal:$False -VerificationLevel:UseSourceVerification

Create a contact to represent the Exchange Online UM Subscriber Access Number
To allow Lync users to call Outlook Voice Access, create a contact to represent the subscriber number Lync users call. You'll need a SIP address (such as [email protected]) and a phone number from your existing pool.

New-CsEXUMContact -DisplayNumber:" +441234567890" -SipAddress:"sip:[email protected]" -RegistrarPool:"lyncpool01" -OU:"CN=Users,DC=company,DC=com"

Next, associate this Exchange UM contact with Exchange Online and grant the new contact the hosted voicemail policy using its SIP address.

Grant-CsHostedVoicemailPolicy -Identity:"sip:[email protected]" -PolicyName:"Exchange Online"

Create the Hosted Voicemail Policy
Next, configure the Hosted Voicemail policy to apply to all end users that are enabled for hosted voicemail by default.

Before configuring this in Lync, we'll need to discover the Exchange Online Authoritative Routing Domain. This is usually your tenant name; for example, <yourtenant>.onmicrosoft.com. If you've changed the default domain in Office 365, it might be different.

Open a PowerShell session and connect to Exchange Online PowerShell. Then run this command:

$cred = Get-Credential
$session = New-PSSession -ConfigurationName Microsoft.Exchange -Authentication Basic -ConnectionUri https://ps.outlook.com/powershell -AllowRedirection:$true -Credential $cred
Import-PSSession $session

Next, run this command to display the Authoritative Routing Domain:

Get-AcceptedDomain | Where {$_.Default -eq $True}

On the Lync Server, use the New-CsHostedVoiceMailPolicy to create a new Hosted Voicemail policy specifying the Exchange Online UM Proxy FQDN and our Authoritative Routing domain for the Organization parameter.

New-CsHostedVoicemailPolicy "Exchange Online" -Destination:exap.um.outlook.com -Organization:<yourtenant>.onmicrosoft.com

Configuring Exchange Online

In Exchange Online, we need to configure the Unified Message features to match the existing on-premises settings; the exception is the contact number we created in the example above. Write down the settings you use, including PIN requirements, country settings and user limits. Log in to the Exchange Admin Center in Office 365.

Creating the Unified Messaging dial plan
After logging into the Exchange Admin Center, navigate to Unified Messaging. On the UM dial plans tab, select add (+) to create a new Dial Plan (Figure 1).

Create new dial plan
Figure 1

In the new Exchange UM dial plan dialogue, enter appropriate details matching those on-premises (Figure 2). If you didn't jot them down on-premises before, or if you missed something, you can refer to the existing on-premises UM dial plan.

On-premises dial plan dialogue
Figure 2

Next, edit the basic configuration to specify the dial-in number end users can dial to access their voicemail. Choose the new dial plan in the Exchange Admin Center and then select Edit (Figure 3).

New dial plan in Exchange Admin Center
Figure 3

Select Configure and, when the dialogue window opens, choose Outlook Voice Access. Scroll down to Outlook Voice Access numbers and add the appropriate Outlook Voice Access numbers as defined (Figure 4).

Outlook Access Numbers
Figure 4

You can alter settings for the dial plan as a whole before saving your changes. The key aim is to ensure you copy all settings from the existing dial plans.

Configure the Exchange UM Mailbox Policy
As part of creating the new dial plan, Exchange creates the Default Mailbox policy and calls it LyncUM Default Policy (Figure 5).

Lync UM default policy
Figure 5

Customize the Exchange UM Mailbox Policy to match the configuration settings of the on-premises policy. If you have more than one policy, create additional ones to match. Our key aim is to ensure that each on-premises policy has a corresponding policy in Office 365.

After creating your policies, make a note of the names you use and record which on-premises policies these correspond to.

Use PowerShell to match up on-premises and cloud policies in Exchange Online
Using the information about matching policies, we'll add configuration settings in Exchange Online that will ensure it's automatically assigned the right policy once the mailbox moves.

Connect to Exchange Online PowerShell and execute the following cmdlet against each UM policy:

Set-UMMailboxPolicy "Lync Default Policy" -SourceForestPolicyNames "Lync On-Prem Default Policy"

The parameter SourceForestPolicyNames indicates that you can specify more than one policy. This is useful if you're consolidating policies as part of an Exchange Online move.

Configuring on-premises Exchange

As Exchange UM is already working on-premises, we don't need to add or remove policies at this stage. What we can do is ensure there's an on-premises mapping that leads to Office 365 policies. This configuration is particularly useful if you need to move a mailbox back on-premises and want UM to be automatically configured.

We'll use our list of UM policies and, using the Exchange Management Shell on an on-premises Exchange Server, use Set-UMMailboxPolicy cmdlets to map policies to their Office 365 equivalents:

Set-UMMailboxPolicy " Lync On-Prem Default Policy " -SourceForestPolicyNames "Lync Default Policy"

Moving UM-enabled mailboxes

With the correct configuration in place, moving UM-enabled mailboxes to Office 365 involves the same processes you'd use to move non-UM mailboxes.

After a mailbox moves, it will automatically be enabled with the correct Exchange UM policy and retain its current PIN, custom messages and other settings.

You may need to wait until the next DirSync cycle completes or manually perform a sync for Lync-related AD settings to update so voicemail redirects to Office 365.

Not much will change from an end-user's perspective. Desk phones using Lync will access voicemail without needing to be reconfigured. The desktop edition of Lync will prompt for credentials like Outlook does after moving a mailbox.

About the author: 
Steve Goodman is an Exchange MVP and works as a technical architect for one of the U.K.'s leading Microsoft Gold partners. Goodman has worked extensively with Microsoft Exchange since version 5.5 and Office 365 since its origins in Exchange Labs and [email protected] 

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