Never lose access to email data
A successful Exchange Online migration depends on maintaining productivity at every stage. ODM gives migration teams the control to provision and configure mailboxes precisely, keep users communicating across tenants, and migrate permissions and delegates throughout the transition.
Highlighted Features
Automate target mailbox provisioning
Migrate accounts to the target with ODM to prepare for your Exchange Online move, or match to existing accounts using defined attributes or a mapping file. During migration, ODM can automatically apply licenses to provision target mailboxes based on available plans in the destination tenant, simplifying setup and reducing manual effort.
Customize mailbox migration options
Configure each Exchange Online migration task to align with your project’s needs, whether migrating all content or selecting specific data. Choose folders, apply date filters, and include recoverable items as needed. Customize settings like inbox rules, permissions, and litigation holds. Decide whether to include Online Archives and migrate content to the primary mailbox, archive, or a specific target folder.
Keep users communicating
Enable calendar sharing between tenants with an Exchange Online migration tool that provides accurate free/busy visibility before, during, and after migration. Automatically enable mailbox forwarding so users continue receiving email in their active mailbox. Migrate permissions and delegates to ensure users retain access to shared mailboxes and remain productive throughout the transition.
Knowledge Center
On Demand Migration Exchange
Keep your users communicating throughout your tenant-to-tenant migration.
On Demand Migration: Desktop Update Agent
Automatically connect your users to their migrated content.
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FAQ
The two methods for completing a cross-tenant Exchange Online migration are performing a mailbox copy or performing a native mailbox move. You should closely research the features and limitations of the two methods to ensure your Exchange Online migration is successful.
The mailbox copy method is popular with many Exchange Online migration tools because it provides better flexibility by having both mailboxes accessible throughout the migration. You can customize the migration scope, merge with existing mailboxes, migrate mailboxes with legal holds, compare source and target data, and perform phased migrations over time while retaining all mailbox permissions. Depending on the solution you use for your Exchange Online migration, you can also update Teams meeting links, provide automation to help end-users update their desktop Office applications, and easily coordinate with other workload migrations like OneDrive, Teams, and SharePoint.
Microsoft does not have a native method for merging two mailboxes, so a common workaround is to configure one of the mailboxes as a Shared mailbox and grant full access to the owner of the other mailbox. However, this requires the user to switch between the two mailboxes to view all the data, and this option is only available if the mailboxes are stored in the same tenant, since you cannot assign mailbox permissions cross-tenant.
If you want to merge two Exchange Online mailboxes, you can accomplish this by copying data from one mailbox to another using an Exchange Online migration tool. Solutions like On Demand Migration include options to copy the content as-is, copy the data to custom folders in the other mailbox, or even copy the data to the online archive of the other mailbox. Once you have all the content migrated into a single mailbox, you can delete the mailbox that is no longer required. When planning to merge mailboxes, it is important to review the settings and size limits of both mailboxes prior to the Exchange Online migration to ensure that the merged mailbox does not exceed its quota.
Many Microsoft 365 subscriptions include features that enable data retention and backup functionality for workloads including Exchange Online. If you just need to retain data for compliance purposes, you can configure retention policies and apply them tenant-wide or to specific mailboxes. You can also enable Litigation Hold on an Exchange Online mailbox or create a custom eDiscovery Hold for the mailbox. These holds will retain all mailbox data even after a user deletes it from their mailbox, and the eDiscovery hold also allows authorized administrators to perform searches against the saved data.
If you just need a one-time backup of a single Exchange Online mailbox to store outside of the tenant, you can consider options like exporting the content to a PST or copying the mailbox to another tenant using an Exchange Online migration tool.
Exchange Online migration is the process of moving email data from one Microsoft 365 tenant to another. It's important because users must maintain continuous access to their email throughout the transition — any disruption impacts communication and collaboration. Beyond day-to-day productivity, migrations must also preserve legacy data including permissions, delegates, shared mailboxes, and public folders to satisfy compliance and legal obligations. Without a structured approach, organizations risk data loss, broken access, and failed compliance audits. A purpose-built solution like Quest On Demand Migration (ODM) ensures the process is controlled, auditable, and minimally disruptive.
ODM keeps users working without interruption through several mechanisms. Automatic mailbox forwarding ensures migrating users always receive email in their active mailbox throughout the transition. Cross-tenant calendar sharing displays accurate free/busy information before, during, and after the migration. Once complete, ODM automatically updates Teams meeting links so organizers retain proper meeting controls. The ODM Desktop Update Agent helps end-users reconnect their Outlook profiles and Office applications to target accounts, eliminating manual reconfiguration and reducing help desk burden.