Coexistence means that there can be multiple Exchange Servers of different versions in the same Active Directory Forest, which can operate with no issues. Although coexistence is allowed, it is a daunting and complex task for the IT administrators. It involves the setup of Exchange Server, configuration, migration of data, and decommission of the old servers. All this must be meticulously planned so that there will be minimal disruption. In this article, we will be discussing the process of installing Exchange Server 2019 in coexistence with Exchange Server 2016 or Exchange Server 2013.
What is needed before Installing Exchange Server 2019?
Before installing the Exchange Server 2019 in coexistence, you must ensure the following:
- The Active Directory schema is updated for Exchange Server 2019.
- The Domain and Forest Functional level must be at a level of at least Windows Server 2012 R2.
- The current Exchange Server 2013 is updated with CU21 or later, or Exchange Server 2016 is updated to CU11 or later.
- The SSL certificates is exported and in hand as these need to be imported.
- DNS is accessible and planning of the changes is to be addressed with the IT administrator.
Stepwise Process to Install the Exchange Server 2019 in Coexistence
Below are the steps to install the Exchange Server 2019 in coexistence.
Step 1 – Preparation of the Active Directory
With the ISO file in hand and mounted, you can run the below command from Command Prompt as Administrator to prepare the Active Directory.
Setup.exe /PrepareSchema /IAcceptExchangeServerLicenseTerms
Setup.exe /PrepareAD /IAcceptExchangeServerLicenseTerms
Step 2 – Install the Exchange Server 2019
Next, you can run the setup to start the installation. After running the setup, follow the prompts, choose the Mailbox Role, configure the destination folder for the installation, and configure the URLs and virtual directories for the Exchange Server.
Step 3 – Install and Configure the Certificates
If the certificate in use in the Exchange Server is a wildcard, it must be exported from the current setup so that it is installed on the new Exchange Server. If the certificate is not a wildcard, then a new certificate must be provisioned. Once the certificate is imported into the Exchange Server 2019, the services, like SMTP, IIS and others, must be assigned.
Step 4 – Check DNS and Updates on Firewalls
The internal DNS server on the Active Directory server is updated automatically with the installation so that both Exchange Servers can work as one. You must discuss with the network team to open the necessary ports for the new Exchange Server 2019. Depending on the protocols you would use, you should only open these to reduce the risk of vulnerabilities and to lock down the system. You can check the ports needed for the Exchange Server 2019 on the Microsoft page.
You must also add the server to the external DNS as the secondary MX record if both servers will remain. In case the old server will be decommissioned, the new server must be placed as a higher priority in the MX record of the external DNS.
Step 5 – Migration of Data
If the configuration is correct and all went well, you can move the mailboxes, archives, and shared mailboxes from one Exchange Server to another.
With regards to public folder, there isn’t a straight-forward method. You need to use a number of scripts to create batches to migrate the public folders. This can be a bit challenging depending on the expertise of PowerShell scripting.
Step 6 – Decommission the Old Exchange Server
The last step is to decommission the old Exchange Server, if you’re fully migrating all your services to the Exchange Server 2019. However, there are some things to consider before doing so:
- Confirm that the primary MX records are in the external DNS.
- Confirm that all the external network ports are pointing to the new server.
- Confirm that all mailboxes and resources have been migrated to the new server.
Once this is complete, you can gracefully uninstall the Exchange Server 2013 or Exchange Server 2016 from the server. Once the Exchange Server has been fully uninstalled, it can be safely decommissioned.
Common Challenges when Installing Exchange Server in Coexistence
Here are some challenges or issues you may face when installing Exchange Server:
1 – Autodiscover Conflicts
You may encounter Autodiscover conflicts, especially with older servers. It might happen that these still respond to Autodiscover requests, which will cause Outlook clients to connect to the wrong server. To resolve this, you can reconfigure the SCP and DNS records to prioritize the Exchange Server 2019 or make sure that these are pointing to the new servers.
2 – Mail Flow Disruptions
Exchange Server works with connectors. A misconfigured connector can lead to email delivery interruption. You should check the Exchange Server 2019 for any connectors which are still pointing to the old server.
3 – Client Connectivity Issues
Clients could have difficulty connecting to the Exchange Server and their mailboxes might be timeouts or disconnected. You must check that the virtual directory URLs are configured correctly and the internal DNS and firewalls are configured properly. Also, you need to make sure that there aren’t any Load Balancers, which are misconfigured.
An Alternative Solution to Migrate the Data
The success of a migration is measured by the data being intact and if there is minimal disruption to the services and business. To migrate the data with minimal disruption, you can use specialized Exchange migration tools, such as Stellar Migrator for Exchange. It can directly migrate the data from one Exchange Server to another, thus helps reduce the downtime and chances of errors.
The tool has an auto-matching feature that automatically maps the mailboxes from the source server to the destination server. It supports cross-forest migrations, delta migrations, and automated public folder migrations.
Apart from Exchange Server to Exchange Server migration, it supports the following scenarios:
Conclusion
Migrating to an Exchange Server 2019 is a strategic move to improve security and compatibility. For this, you can install Exchange Server 2019 in coexistence with your existing server (Exchange Server 2013 or 2016). For successful installation of Exchange Server 2019 in coexistence, you should plan well and also consider the risks and challenges involved. As migration of data is an important step, you can keep a right Exchange migration tool in hand for migrating the data. Stellar Migrator of Exchange is one such tool that can automate and streamline the process of migrating the data from one Exchange Server to another.
