For a successful migration, a configured and working Hybrid configuration must be in place between your source Exchange environment and the Microsoft 365 tenant. To ensure these prerequisites are met, we suggest working through the following checklist. Once each question can be answered with "Yes," proceed to the next step in the guide.

• Creation of Microsoft 365 tenant with domain (Namespace) configuration is completed.
• Microsoft Entra Connect is set up and configured to include all Organizational Units where Mailbox accounts that will be migrated exist.
• The Hybrid Configuration Wizard has been run successfully, meaning that all aspects of the connectors have been configured. This extends to the Mail Flow Connectors/Federation and MRS Endpoints.
• Mail flow to the migrated account is working successfully, with an MX record pointing either into Exchange Online Protection or still On-Premises, depending on your desired cutover state.
• The MRS EndPoint is accessible from inside Microsoft 365, meaning that a test of a single mailbox into the Microsoft 365 tenant has been completed.
• The use of auto-discovery and upload process functions requires a Source with Exchange 2013 and after. System with Exchange 2010 will require the steps of importing a CSV file found here to upload users and settings.
• Modern Authentication is now the default authentication method to be used with MigrationWiz and Exchange Online due to Microsoft discontinuing support for Basic Authentication in Exchange Online at the end of December 2022. The following Microsoft documentation outlines this change in more detail. Should you have additional questions on how this change may impact your tenant, please contact Microsoft to assist with providing that information: Deprecation of Basic authentication in Exchange Online

The Prerequisites section below offers more detail on how this can be achieved, with links to the various Microsoft articles that facilitate this.

Prerequisites

When starting a Hybrid migration project with MigrationWiz, there are a number of prerequisites that need to be completed in your environment before launching the migration. These prerequisites relate to the health and setup of the Exchange and Office 365 tenant and ensure that the system can connect and migrate effectively.

1. The Microsoft 365 Tenant has been created and a valid domain/namespace has been configured.

The Microsoft 365 tenant should have been created and set up with the correct domain name, matching the on-premises system. Tenant configurations can vary greatly depending on the type of implementation you are performing, but the base configuration should be in line with the on-premises Exchange environment that you are migrating from.

2. Microsoft Entra Connect is installed and syncing identities to the Microsoft 365 tenant.

Having valid identities inside the Microsoft 365 tenant is a vital step in the process as it provides the linkage between the on-premises and the cloud-based implementation. For details on how the Microsoft Entra Connect is set up and configured, check the Microsoft documentation.

3. Hybrid Configuration Wizard has been run and completed successfully. 

This Microsoft Documents article contains all the setup and configuration information that is required for creating a Hybrid environment. The full list of prerequisites can be found here.

4. Access to the MRS (Mailbox Replication Service) endpoints is configured and working. 

The MRS endpoint configuration is performed during the Hybrid Configuration Wizard process. Once this is created, and you have connected to the Microsoft 365 tenant PowerShell, it can be tested with the following instructions.

For instructions on how to connect to Exchange Online Powershell use this link

Run the Test-MigrationAvailability cmdlet, specifying the endpoint as your configured version.

Test-MigrationServerAvailability -Endpoint "Hybrid Migration Endpoint - EWS (Default Web Site)" 

The output will respond with a Success/Failure message similar to below. 

RunspaceId      : 785717df-80ce-4148-baff-2b6aad962bfb 
Result          : Success 
Message         :  
SupportsCutover : False 
ErrorDetail     :  
TestedEndpoint  : Hybrid Migration Endpoint - EWS (Default Web Site) 
IsValid         : True 
Identity        :  
ObjectState     : New 

 In the event of a failed state, the Hybrid Troubleshooting steps on the Microsoft site are useful in ascertaining the issue. 

5. A test migration of a single mailbox has been completed successfully using the native toolset. 

To confirm that everything is indeed working exactly as expected, we recommend performing a single mailbox migration, using a test or pilot mailbox, which can be run manually against the infrastructure. This checks that the entire end-to-end Hybrid environment that has been set up is migrating data, performing look-ups for Free/Busy status, providing correct mail flow, and verifying address book lookups.