Provisioning Exchange Online for Lync Hybrid Part I

In a previous blog article, we walked through the steps to deploy an Office 365 Lync Hybrid solution with Shared SIP Address Space. We also created some Lync users hosted on-prem and some hosted on-line. However, since no Exchange on-prem servers were deployed, all user mailboxes can only be hosted on the Office365 E3 plan. This post is the first of a two-part series where we continue to build on the hybrid environment and walk through how to configure Exchange Online to work with Lync Hybrid and how to properly provision user mailboxes that can provide email services to Lync users. Lets recap on the architecture again as shown in the diagram:

1. Provisioning Exchange Online Mailboxes
As always, every Exchange mailbox requires an AD account. Since we are using Lync Hybrid, we do not create accounts on the tenant directly. Instead, we create the account on our on-prem AD and let DirSync create the corresponding account in the tenant. When creating a new user in AD, make sure to use the shared SIP address space domain for the UPN, otherwise DirSync will not work correctly. Below is a screenshot of a new user "Cammie Cheng" created on the on-prem AD:

As we have not yet enabled the user for Lync, we can proceed to enable the user for Lync on-prem first, before moving the user to Lync Online if desired. Simply use the Lync control panel to enable the user and once that is done, note that the msRTCSIP-PrimaryUserAddress and proxyAddress attributes will then be populated with the users' SIP address:

We are now ready to synchronize the new user with O365. By default, DirSync will perform synchronization every 3 hours but we can manually force sync using windows powershell. On the ADFS computer, import the "DirSync" module and run "Start-OnlineCoexistenceSync":

After a few minutes, the new user will appear in the Office365 Active User list. At this stage, the user does not have Exchange online mailbox yet because we have not assign the appropriate licenses. We can do that by clicking the "Edit" button:

After assigning a location and E3 license for the user, we can see the O365 is creating a new mailbox for the use. This can take a couple of minutes:

By default, O365 will create an email address of username@mydomain.onmicrosoft.com as shown below on the left. This is obviously not desirable as we want to use the shared SIP address space as the email address domain. So we run ADSIEDIT to modify the user's proxyAddress attribute to add the desired SMTP address as shown below on the right: 

After this, we start the DirSync process again and when completed, the desired email address for user will be assigned in the O365 admin portal. We can proceed to let the user login to O365 via the portal to access his/her email and calendar. Note that when signing into the portal with the shared SIP address space, we will actually be redirected to the ADFS login page before returning back to O365:

By entering the user's onprem AD credentials, O365 will then authenticate the user via ADFS and redirect the user back to the O365 welcome page since we are logging in for the first time. The email inbox and calendar is now accessible as shown below. The welcome screen allows the user to install the Office Suite locally on the PC if desired.

2. Configuring on-premises Lync Server 2013 integration with Exchange Online
In order to enable our on-prem Lync server to integrate with Exchange online, we need to already have a shared SIP address space with our O365 tenant, which we have already done in the previous article. Next we create a new hosting provider on our Lync edge server for Exchange online using the New-CsHostingProvider cmdlet as shown below:

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

We then ensure the management store replication has completed to the Edge server by running the Get-CsManagementStoreReplicationStatus cmdlet. This completes the Lync on-prem integration with Exchange online. In the next article, we will walk through how to enable Lync on-prem users voice mail on hosted Exchange UM.