Migrating a small organization from Exchange 2010 to Exchange 2016 (Part 5)

If you would like to read the other parts in this article series please go to:


During the last part in this series we completed the post installation configuration of Exchange Server 2016 and configured it as per our basic design, then performed some basic tests to ensure it functions correctly. We’re now ready to update the mail routing to the Exchange 2016 server in preparation for the migration. We’ll also integrate with an Office Online Server as an optional step before migration to allow documents to be previewed within Outlook Web App.

Migrating Mail Routing

Updating Inbound Mail Routing

In the previous article, we tested to ensure that our Exchange 2016 server can receive mail and deliver it to Exchange 2010 users. By default, Exchange Server 2016 is already configured to receive email from the Internet using Anonymous permissions on the default receive connector.

If this hasn’t been changed from the defaults, update either firewall rules to direct traffic on SMTP port 25 to the Exchange 2016 server, or update your spam filter appliance to do so.

After this change has been applied ensure that inbound mail flow is not interrupted before moving on to migrating outbound mail flow.

Updating Outbound Mail Routing

With incoming mail now flowing through Exchange 2016, our next step is to make the changes required to allow and then reconfigure Exchange Server 2016 to be responsible for outbound mail flow rather than via the Exchange 2010 server.

In our example environment our mail flow is direct to the Internet, but in your organization you might use a spam filter appliance. Therefore, make sure if you use a smart host for relay, ensure the IP address of the new Exchange 2016 server is added as a server allowed to relay outbound messages.

Likewise, if you email direct to recipients then ensure the Firewall rules allow the Exchange 2016 server IP address to initiate connections to Internet hosts on TCP port 25 without tampering (such as SMTP Fixup).

After ensuring that the Exchange 2016 server is allowed to relay outbound mail, we are ready to update the Send Connector. To perform this step, open the Exchange Admin Center and navigate to Mail Flow and then choose Send Connectors. You should see the Send Connector used for outbound mail flow within the list:

Figure 1: Locating the primary Send Connector for outbound email

Open the properties for the Send Connector used for outbound mail flow.

Navigate to the Scoping tab and locate the Source server section. The Exchange 2010 server should be listed. Choose Add (+) and select the Exchange 2016 server, then select the Exchange 2010 and choose Remove (-); leaving only the Exchange 2016 server within the server list:

Figure 2: Updating send connector settings

After verifying both the server IP address is listed as able to relay, and that the correct Exchange 2016 server has been selected, choose Save to apply the configuration.

As with updating inbound mail routing, ensure you test outbound mail flow is unaffected before continuing.

Installing Office Online Server

Optionally, before migrating mailboxes we can install Office Online Server. At the time of writing, this is still in preview and is expected to reach general availability (GA) around the same time SharePoint Server 2016 is launched.

The Office Online Server is required for viewing and editing attachments within a web browser, so for our small organization we will walk through the installation of a single server farm. For larger organizations, high availability may be required.

Installation of Office Online Server

The current version of Office Online Server, the preview version, can be downloaded from this Microsoft link.

This must be installed on a standalone Windows 2012 R2 virtual machine or server. Before commencing the install we must also install a number of pre-requisites. First install the Visual Studio 2015 runtime from this link.

Next, install the .Net Framework 4.5.2, then install all available Windows Updates.

Finally, before commencing the installation, use the following PowerShell script to install all required pre-requisites, as shown below:

Install-WindowsFeature Web-Server, Web-Mgmt-Tools, Web-Mgmt-Console, Web-WebServer, Web-Common-Http, Web-Default-Doc, Web-Static-Content, Web-Performance, Web-Stat-Compression, Web-Dyn-Compression, Web-Security, Web-Filtering, Web-Windows-Auth, Web-App-Dev, Web-Net-Ext45, Web-Asp-Net45, Web-ISAPI-Ext, Web-ISAPI-Filter, Web-Includes, InkandHandwritingServices

Figure 3: Installing OOS server pre-requisites

After installation of pre-requisites, perform a re-boot.

Next, mount the ISO image downloaded for installing Office Online Server and then start setup. For our installation, we’ll leave all defaults as-is. In the preview you will note that the version of Office Online Server is 2013. This is expected:

Figure 4: Installing Office Online Server.

Configuration of Office Online Server

After installation completes, Office Online Server will not be available for use. To make it available for use with Exchange Server 2016 we must install a new Office Online Farm.

Before we do that, we’ll need to install a valid SSL certificate and configure a DNS name.

The standard naming for Office Online Server is oos.domain.com. We will choose to use oos.stevieg.org for both the internal and external URLs for our simple farm.

We’ll use the Manage Computer Certificates management snap-in to import the SSL certificate and check the certificate Friendly Name. Search in the Windows 2012 R2 Start Menu, then launch the snap-in:

Figure 5: Locating Computer Certificates

You should see Certificate – Local Computer launch. Navigate to Personal and right-click Certificates. Choose All Tasks>Import… and import your certificate.

Figure 6: Importing an existing SSL certificate

In our example we’ve imported an example Wildcard certificate. We’ll navigate to Certificates and record its Friendly Name from the list.

Figure 7: Checking the Friendly Name of the SSL certificate

You’ll note from the command below that we specifically need to enable editing of documents when creating the farm. This is dependent on whether or not you have appropriate Office licensing. We are choosing to enable it in the example below:

New-OfficeWebAppsFarm -InternalURL “https://<OOS FQDN>” -ExternalURL “https://<OOS FQDN>” ” -CertificateName “<Certificate Name>” -EditingEnabled

Figure 8: Creating a new Office Online Server Farm

Configuration of Exchange 2016

To ensure that Exchange Server 2016 can utilize our new Office Online Server farm we must configure the discovery endpoint using PowerShell. This can be configured at the Mailbox server level, or the organization level. It is useful to configure at the mailbox level if you need to maintain co-existence with Exchange 2013.

As we are upgrading from Exchange 2010, we can simply configure the endpoint at the organizational level with the Set-OrganizationConfig cmdlet and then restart the OWA app pool on our single server, as shown below:

Set-OrganizationConfig -WacDiscoveryEndpoint https://<OOS FQDN>/hosting/discovery

Restart-WebAppPool MsExchangeOwaAppPool

Figure 9: Configuring Exchange 2016 to use the Office Online Server

Testing Office Online Server with Exchange 2016

Finally, we’ll need to make sure that document viewing and editing works as expected. If all is configured correctly, then viewing an email with an attachment should present the View option against an attachment:

Figure 10: Checking integration of OOS

If you don’t see the option it may simply be that after making the Organization configuration change, Active Directory had not replicated before re-starting the OWA app pool and attempting access.

When you see the view option, simply select it to switch to view mode. If you’ve also enabled Editing in the Office Online Farm, you’ll see the Edit and reply option as well.

Figure 11: Viewing attachments using OOS

By selecting Edit and reply, you will be able to compose a reply and edit the document before sending. If the configuration is correct then you should see the full Office Online in editing mode displayed:

Figure 12: Editing attachments using OOS


In this penultimate part in the series we’ve migrated mail routing across from Exchange 2010 to Exchange 2016, and we’ve installed Office Online Server (if required) to allow viewing and editing of attachments in Outlook Web App. In the final part of this series we will migrate mailboxes, then decommission Exchange Server 2010.

If you would like to read the other parts in this article series please go to:

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9 thoughts on “Migrating a small organization from Exchange 2010 to Exchange 2016 (Part 5)”

  1. Having problem with send connector. One thing I notice is 2016 exchange only shows mailbox role, while 2010 show mailbox, clientaccess, hubtransport.

  2. do i have to remove the exchange 2010 after selecting the send and receive conns ? or can they both stay until i finish moving mailboxes ??

    1. just one more thing…does this look right,,i notice the new server only says mailbox under roles,,, not client access , hub transport like the 2010 does,,,is this right? or am i missing something, we dont use public folders…

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