Microsoft 365 Tenant to Tenant Coexistence

CloudM Migrate Microsoft 365 tenant to tenant coexistence enables you to migrate end users in batches while maintaining email and calendar connectivity between the domains as data is moved. End users are migrated with full coexistence capabilities, including free / busy.

CloudM Migrate tenant to tenant coexistence offering includes the creation of mail-enabled contacts for mail-flow, and calendar coexistence for free / busy scheduling.

Coexistence is only supported for the tenant to tenant migration scenarios in which the domain name differs.

Azure Active Directory Connect (ADFS, AADConnect, AADSync, ADSync, etc.) cannot be used to do anything with the destination user accounts until after the migration project is fully completed.


  • At this time, we are not able to support tenants that have enhanced security set up.  
  • Migration projects must be fully licensed in order to proceed with the migration.
  • Only specific Microsoft 365 licenses are supported for this migration.  The supported types are listed in the Platform Configuration and Provisioning drop-down menu.
    • If using CloudM Migrate to provision destination accounts, only one Office 365 license type can be used per configuration.
    • The Microsoft 365 license types can be modified at any point during the migration project,
  • It is recommended that the administrator account on the destination must use the onmicrosoft domain and not the vanity domain.
  • It is recommended the administrator accounts on both the source and the destination have an Office 365 license applied and be set up with a mailbox before the migration project is created.
  • The migration can be completed in batches; however, all the users need to be in the same project.
  • Once a project is set up, you can use the Check Coexistence option in the Office Tenant to Tenant to add/remove users from the project.  
  • Cloud accounts are created on the destination. 
    Note: User passwords created as part of the migration are defined using the Password field within the Items list

Configure your CloudM Migrate Project for coexistence enabled migration

Source Platform

Configure your source Microsoft 365 platform as per Microsoft 365 Configuration.

Destination Platform

Configure your destination Microsoft 365 platform as per Microsoft 365 Configuration.

Select Items to Migrate

From the Actions menu, select Get items from source.


This will populate the items with objects from the Source environment.

Configure Migration Settings

Configure your migration date ranges as required. For more information see General Migration Settings.

Environment Scan

If required, run an environment scan. For more information see Environment Scan.

Configuring Coexistence 

From the Summary screen, click the notification:

Click Enable Coexistence to start the process:

CloudM Migrate will now perform a series of checks and begin configuring your environment for Coexistence migration.

CloudM Migrate will create the following:

  • Mail contacts for source accounts in the destination
  • Organisational relationship between destination environment and source environment, with calendar free/busy enabled
  • Organizational relationship between source environment and destination environment, with calendar free/busy enabled

Closing the setup screen does not stop coexistence setup. You can always return to the setup screen by clicking the notification on the summary step

Once complete you will see a notification on the summary screen 

Once completed you will be able to successfully migrate users while maintaining mail and calendar coexistence.

Post Migration 

Once your migration has completed, you are able to remove the imported contacts by returning to the Coexistence setup screen, and clicking Clean up Imported Contacts.

This will remove the imported mail contacts from the destination environment. The cleanup process removes all imported mail contacts and removes the Organisational rules that configure calendar free-busy. 

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