Success story
Hybrid Exchange Server to O365 migration in multi-forest Active Directory environments
Challenge
Our client Petit Palace Hotelity, a growing company, was in a complex environment with multiple Active Directory forests and a Microsoft Exchange architecture spread across multiple domains. This type of infrastructure is not common, as for security reasons and due to several acquisitions over the years, the organization had kept user forests and Exchange resource forests separate. In this case, they were using a Resource Forest model with Linked Mailboxes to manage user emails. This approach, while effective in terms of security and administration, presented significant challenges when the company decided to migrate to Office 365 (O365) to take advantage of the benefits of the cloud.
“We have made Uniway the main technological partner of reference in our company. In addition to their outstanding quality in monitoring, prevention, security, support, organization and execution of tasks, we even decided to hand over to them the entire management with the suppliers and manufacturers of the Solutions we use (including the final on-site support).”
Pedro Sánchez
CIO Petit Palace-Hotelatelier
Customer context
Hybrid migrations from Exchange to O365 are technically challenging in standard scenarios, where a single Active Directory forest is used to manage the Exchange infrastructure. However, in a multi-forest environment with multiple Exchange domains and resource forests, the challenges multiply. In this particular case, the migration not only had to consider synchronization between the on-premises and O365 environments, but also the consolidation of Active Directory and the removal of the Exchange Resource Forest, which adds a significant layer of complexity.
Approach and solution
Our team of Microsoft Exchange and Office 365 migration experts developed a comprehensive technical approach to ensure the migration was successful, minimizing operational impact and ensuring continued coexistence between on-premises and O365 environments. Below we outline the key aspects of our solution:
- Infrastructure analysis and planning: The first step was to perform a thorough analysis of the existing Exchange infrastructure, both in the user forests and in the resource forests. We identified the dependencies and communication flows between the Active Directory and Exchange Server forests, and designed a detailed plan for the migration that addressed both identity synchronization and coexistence configuration.
- Hybrid coexistence: We implemented hybrid coexistence between the on-premises Exchange servers and the O365 tenant, using Hybrid Exchange to enable mailbox coexistence in both the cloud and on-premises. This approach allowed users to continue using their on-premises mailboxes while we gradually migrated emails to the cloud. Additionally, we set up identity synchronization using Azure AD Connect, ensuring that user accounts and Active Directory objects were properly replicated in the O365 environment.
- Gradual Mailbox migration: We implemented a phased migration of Exchange mailboxes to O365. Since the Exchange infrastructure was divided into several forests, we used Exchange Online Migration with the option of "Cutover" or "Staged Migration", depending on the specific needs and characteristics of each group of users. In this way, we managed to migrate mailboxes without interrupting user productivity and ensuring that the transition was as smooth as possible.
- Active Directory consolidation: Active Directory consolidation was one of the biggest challenges in this project. Because multiple AD forests existed, we established a strategy to merge data and simplify the Active Directory structure. We implemented advanced migration and synchronization tools, and created a process for phasing out the Resource Forest, allowing all users to be consolidated into a single Active Directory without compromising security or data integrity.
- Decommissioning the Resource Forest: One of the key goals of the project was to decommission the Resource Forest that managed the resource mailboxes. This required a careful migration of all data associated with the resource mailboxes and their integration within the new unified O365 environment. As mailboxes were migrated, the Exchange systems in the Resource Forest were decommissioned , removing dependencies on this old environment..
- Security and compliance management: Throughout the process, a strict focus on security and compliance was maintained. We ensured that data protection policies and internal company regulations were respected, to protect migrated data in the O365 environment. We also implemented proactive monitoring to detect any security issues during the migration process.
Results
Thanks to our expertise in hybrid Exchange and O365 migrations, the client achieved a successful migration, with no service interruptions and a gradual and controlled transition. The coexistence between the Exchange Server and O365 environments allowed employees to continue working seamlessly during the migration, while the consolidation of the Active Directory and the elimination of the Resource Forest optimized user management and reduced operational complexity.
Key Customer benefits:
- Controlled and seamless migration: Hybrid coexistence enabled a gradual migration without impacting employee productivity.
- Infrastructure consolidation: Consolidating Active Directory forests and eliminating the Resource Forest streamlined administration and reduced operational costs.
- Security and compliance: Advanced security and compliance solutions were implemented in O365, ensuring data protection during and after migration.
This success story demonstrates how a hybrid migration from Exchange Server to O365 can be effectively performed, even in complex multi-forest environments, through strategic planning, appropriate tools, and a detailed technical approach.