Office 365 to Hosted Exchange Migration

Use EdbMails to migrate Office 365 mailboxes to a supported Hosted Exchange environment after the destination mailboxes and access requirements are prepared. The migration workflow connects to Microsoft 365 with modern authentication, connects to the Hosted Exchange target with the connection method supported by the provider, maps source and destination mailboxes, and records migration progress in the EdbMails logs. Plan the target quotas, message-size limits, DNS cutover, and user access with your Hosted Exchange provider before the production migration.

If you are comparing this scenario with other Microsoft 365 migration paths, review the Office 365 migration tool for the broader EdbMails migration workflow.

The migration direction on this page is Office 365 to Hosted Exchange. Prepare the Hosted Exchange destination before migration and confirm provider-supported connection details, mailbox quotas, message-size limits, and user-access requirements.

Use the planning, preparation, migration, and post-migration checks below to validate the destination before the final mail-flow cutover.

1. Plan an Office 365 to Hosted Exchange migration

   Before migrating, confirm what will move, how the Hosted Exchange destination will be prepared, and when mail flow will switch to the new provider. A pilot migration with a small set of mailboxes can help validate connectivity, mapping, target quotas, message-size limits, and user access before the production move. Before the production move, use the Office 365 migration checklist to confirm tenant access, mailbox readiness, network planning, and cutover preparation.

   1. Inventory the Office 365 mailboxes and supported mailbox data that must be migrated.
   2. Record mailbox sizes before scheduling the production migration.
   3. Identify shared, archive, or public-folder workloads that need separate preparation.
   4. Confirm the Hosted Exchange provider supports the required Exchange/EWS connectivity.
   5. Obtain the destination server or Autodiscover details and credentials required by the provider.
   6. Confirm destination mailbox quotas and message-size limits.
   7. Create and license the required target mailboxes before migration.
   8. Prepare target public folders where applicable.
   9. Decide whether to migrate all selected mailboxes in one production window or in smaller groups.
   10. Plan a final incremental pass where appropriate.
   11. Check network capacity and service limits that can affect throughput on both environments.
   12. Run a pilot migration and validate connectivity, mapping, migrated content, Outlook connectivity, and mail flow.
   13. Plan DNS and user communication changes with the Hosted Exchange provider. Do not change MX or Autodiscover records until the target and cutover plan are ready.
   14. Keep the source Microsoft 365 tenant and licenses available until validation and any final follow-up migration are complete.

2. Prepare the source Office 365 tenant and target Hosted Exchange server

   On the source Office 365 server:

   1. EdbMails connects to the Office 365 source with modern authentication. Use Auto Registration when a Global Admin account is available for EdbMails application registration in Microsoft Entra ID. If your organization uses Manual Registration, follow the current EdbMails manual-registration procedure and use an account that meets the documented mailbox-access requirements.
   2. Confirm that the source tenant is accessible and that the EdbMails computer has a stable connection to both environments. Ensure that your network and bandwidth meet the requirements for the migration.

   On the target Hosted Exchange server:

   1. Create the destination mailboxes before migration and assign the service plan or license required by your Hosted Exchange provider.
   2. Obtain the provider-supported connection details, including Autodiscover or the Exchange server name, Exchange version where required, and the credentials or permissions needed to access the destination mailboxes. For multiple-mailbox migration, use the EdbMails connection method that matches your environment.
   3. Confirm mailbox quotas, message-size limits, and any provider-controlled EWS throttling before the production migration.

3. Steps to migrate Office 365 to Hosted Exchange server

   1. Step 1: Download and install EdbMails Office 365 migration software

      • Download and install the EdbMails application on your computer.

        

         See a detailed list of EdbMails system requirements for Office 365 to Hosted Exchange migration.

   2. Step 2: Launch EdbMails Software

      • Enter the required details and click the 'Login' button, or select 'Start Your Free Trial' to access the EdbMails application.

        

      • Select ‘Office 365 Migration’ as migration option from the products list

        

      • Choose the option 'Office 365 to Live Exchange Migration'.

        

      • Keep the default job name or click the ‘New Job’ button to give it a name of your choice.

        

   3. Step 3: Connect to the source Office 365 server

      • Click the 'Add New Connection' button to create a new connection to the source Office 365. If you'd prefer to use a previous connection, choose it from the connection list and click the 'Connect to Existing' button to continue.

        

      • Select the required connection option and click the ‘Next’ button to proceed.

        

      • Select one of the available methods for secure OAuth 2.0 modern authentication.
      • Click the ‘Login’ button to continue.

        

      • Create a new Office 365 source connection or reuse an existing connection. Select Auto Registration or Manual Registration based on your organization's EdbMails and Microsoft Entra ID configuration. Complete the Microsoft sign-in process using an account that meets the requirements for the selected registration method.

        

      • Once authentication is successful, select a method to load the mailboxes. Alternatively, you can load and migrate mailboxes using a CSV file.

        

   4. Step 4: Select the mailboxes for migration

      • DIf all required mailboxes are not displayed automatically, use the supported CSV or saved-list option to load and select the required source mailboxes. For larger environments, use the CSV file option to load additional mailboxes.
      • Select the mailboxes you want to migrate from the left pane, then click ‘Next’ button to continue.

        

        Tip: If this is the first time you’re migrating with EdbMails, the migration is a full migration. On subsequent migrations from the same source to the target, the migration is incremental.

   5. Step 5: Connect to target Hosted Exchange server

      • Click the 'Add New Connection' button to create a new connection to the target Hosted Exchange server. If you'd like to use an existing connection, select it from the list and click 'Connect to Existing' to proceed.

         With EdbMails, you can migrate mailboxes, public folders, and archive mailboxes from Microsoft 365 to Hosted Exchange server.

        

      • Select the ‘Connect to Hosted Exchange server’ option.
      • Click the ‘Next’ button

        

      • Choose the appropriate option to connect to your target Hosted Exchange server and click ‘Next’ to continue.

        

          Click here to know more details about various methods to connect to Hosted Exchange server

      • You can use the ‘Connect Using Autodiscover Email’ option if you want to connect using an email address and password enabled with the Autodiscover service, or choose ‘Default Connection’ to connect using the Exchange server's domain name or IP address.

        

      • Enter the target Hosted Exchange server login details and click the ‘Login’ button

        

      • Select one of the methods to load the mailboxes.

        

   6. Step 6: Map source and target mailboxes

      • Select the appropriate mapping option.

        

         Click here know about user-defined mailboxes / folders mapping
      • EdbMails automatically maps mailboxes and folders between the source and target servers, which is especially useful for large-scale migrations. Alternatively, you can manually map source folders and subfolders to specific target locations as needed.

        

   7. Step 7: Start Office 365 to Hosted Exchange migration

      • After completing the mailbox mapping, click the ‘Start Migration’ button to proceed.

        

      • You can track the migration progress in real-time, and a confirmation message will appear once it's complete.
      • Click on ‘View Log’ to review the detailed migration report. You can also sign in to the target Hosted Exchange server to confirm that all items have been successfully transferred.

        

4. Post-migration checks for Hosted Exchange

   1. Step 1: Validate migrated data and complete the final incremental pass

      Check representative mailboxes on the Hosted Exchange target and review EdbMails logs for failed or skipped items. If users continued working in Microsoft 365 during the migration window, run the planned follow-up migration before changing mail flow.

   2. Step 2: Update mail flow, Autodiscover, and Outlook

      When the target has been validated, update MX and Autodiscover records using the exact DNS values supplied by the Hosted Exchange provider. Do not copy generic Microsoft 365 DNS values. Test mail flow and update or recreate Outlook profiles when required so users connect to the new Hosted Exchange mailboxes.

   3. Step 3: Retire Microsoft 365 services only after validation

      Do not remove source permissions, domains, or Microsoft 365 licenses until validation, the final follow-up migration, DNS cutover, and user-access checks are complete.

5. Office 365 migration troubleshooting

    See the troubleshooting solutions for Office 365 to Hosted Exchange migration. For more details about EdbMails Office 365 migration, see the frequently asked questions. For the end-to-end migration sequence, use the Office 365 migration guide to review source connection, mailbox selection, mapping, migration, and verification.

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Additional resources:

• EdbMails Office 365 migration tool
• Office 365 Public folder migration
• Office 365 Archive mailbox migration
• Office 365 Public folder to Shared mailbox migration
• Setting custom throttling policies on Exchange server
• Office 365 mailbox migration guide