How to Migrate On-premises Exchange Mailboxes to EXO (Exchange Online)

Moving from on-premises Exchange Server to Exchange Online is a strategic move for the businesses where they get the subscription-based infrastructure and email/collaboration as a service. They also get all the security stacks that Microsoft can offer on the cloud platform to increase scalability while taking advantage of the modern collaboration tools available.

In this article, we will be discussing different ways you can follow to migrate from an Exchange Server to the Exchange Online (EXO), depending on the migration size and other factors.

Reasons for Migrating to Exchange Online

There are a number of reasons why you would move to the cloud for email and collaboration services. Let’s list a few common ones.

• Exchange Online provides seamless and secure access to email, OneDrive, SharePoint, and others. All the tools of Microsoft 365 are accessible from anywhere and any device.
• Continuous updates as the infrastructure is maintained and updated by Microsoft, along with introduction of new features and tools.
• There is no limit on the scalability of the system as you can scale up and down depending on the needs.
• There will be no cost of hardware upgrade, maintenance, and energy.

Methods to Migrate On-Premises Exchange Mailbox Data to EXO (Exchange Online)

There are a number of methods to choose from to migrate mailboxes from on-premises Exchange to Exchange Online. Below, we have mentioned the most common ones, along with their pros and cons.

1: Cutover Migration

Cutover migration is the process that involves the change of services and migration of data, all in one operation. In this, you can update the DNS records to point to Office 365 and immediately start using the Exchange Online. This would be ideally done during a weekend or on a holiday when the activity of the business is minimal or will not create disruption in the operations.

This kind of approach is ideal for small businesses and requires precise planning. You need to change the MX records (which take care of routing emails) and immediately start the migration of data. After the change of records, the users will be able to access their online account while their data will be migrated afterward.

Migration of data requires manual intervention where you would need to export the data from mailboxes, archives, shared mailboxes, and public folders to PST. You can use the New-MailboxExportRequest command in the Exchange Management Shell to migrate mailboxes. For public folders, you can use either Outlook or migration scripts.

There are some disadvantages of this method, which include downtime, big margin of error, longer migration time, and manual intervention. The upside of using cutover migration is that it is fast and simple to switchover.

2: Hybrid Migration

The hybrid model is designed especially for large businesses that have a longer migration deadline. Migration of data takes longer when you compare with other migration methods. The idea of hybrid model is to have both the local Exchange Server and the Exchange Online act as one server.

The below prerequisites are imperative for a successful hybrid migration:

• The Exchange Server is fully supported as per the Microsoft KB.
• The Exchange Server is fully updated to the latest Cumulative Update.
• The Exchange Web Services (EWS) are fully operational.
• The certificates are in hand with all the credentials.
• Access to the DNS records of the domain.

The process involves four steps:

1. Setup the Entra AD Connect to establish synchronization of the current identities with the cloud. This will serve as a single-sign on method for the users.
2. The second step is to configure the Hybrid Configuration Wizard (HCW). This will connect the two platforms with send connectors and other configuration.
3. Once this is complete, a connection is established between the local server and Exchange Online. So, you can start the data migration. This can be done using the New-MoveRequest command in the Exchange Management Shell (EMS). Once complete, you can just complete the move and do one last migration. After this, the users will seamlessly connect to the Online resources with minimal intervention. To migrate public folders, the migration task is a bit more complicated as there are a number of scripts involved and requires preparation of the local public folders, validation of the hierarchy, and then completing the migration process.
4. The last step is to change the DNS records to point to the MX record and other records on the Exchange Online.

This approach is seamless and the users will not even know that their mailboxes are being migrated. It is the smoothest migration method, but it is also the most complicated and slow migration. If all goes well, there shouldn’t be any major issues. However, there could be synchronization and operational issues that would delay the migration effort.

3: Using Specialized Exchange Migration Tool

Both native methods have their pros and cons. If not planned well or the wrong method is used, it can lead to delays and other issues. You can consider Stellar Migrator for Exchange - a specialized Exchange migration tool that can reduce complexity and offers a number of options for data migration. It can migrate data from a local Exchange Server to another local server or Exchange Online, Exchange Online tenant to another tenant, and from Exchange Online to local Exchange Server.

It is a powerful and yet simple tool that can fulfill all the migration needs with guaranteed data integrity and peace of mind. It offers mailbox and public folder migrations with cross domain and cross forest migrations.

By choosing Stellar Migrator for Exchange for your migration, you will be able to reduce the gap when it comes to complexity and make your migration task simpler, faster, and a secure one.

Conclusion

Migrating from a local Exchange Server to Exchange Online has a lot of benefits, but it is a daunting task if not planned well. The transition to cloud service requires careful planning, approval from the management, and precise technical execution. When it comes to migration of data, you should choose the right tools. Stellar Migrator for Exchange is a perfect tool when it comes to migrating data from local Exchange Server to Exchange Online (Microsoft 365) with complete integrity and in minimum time.