Exchange Online (Microsoft 365) to Exchange Online (Microsoft 365) Mailbox Migration Guide
This guide contains all the necessary steps for migrating email data from one Microsoft 365 instance to another Microsoft 365 instance.
12/15/202410 min read
MigrationWiz
MigrationWiz is not a sync tool. Items already migrated and updated at the source mid-migration will not be updated at the destination.
MigrationWiz supports the capability to share migration projects across a Workgroup. When the Project Sharing feature is turned on, all active agents can view all migration projects.
First Time?
If this is your first time performing a migration, we have created a Migration Planning & Strategy Guide to walk you through planning, set-up, and general migration best practices. If you have never performed a migration before, we suggest reading that before beginning the steps outlined in this scenario.
Prerequisites
It is important to highlight and meet the following prerequisites for a smooth migration project.
Licensing
Purchase and apply User Migration Bundle licenses for all the users being migrated. For this migration type, we suggest the User Migration Bundle. For questions on licensing, visit MigrationWiz Licenses.
User Migration Bundle Licenses have unlimited data available per license.
User Migration Bundle Licenses are applied to the customer's users and expire 12 months after their purchase date.
Document, Personal Archive, and DeploymentPro projects are all included when using User Migration Bundle Licenses.
This license type must be applied manually.
To use your license by following the next steps:
Purchase Licenses.
Create a Customer.
Apply Licenses.
Review Considerations.
Purchase Licenses
In the top navigation bar, click Purchase.
Click the Select button and choose User Migration Bundle licenses.
Enter the number of licenses you want to purchase. Click Buy Now.
Enter a Billing address if applicable.
Click Next.
Review the Order Summary and enter a payment method.
Click Place Your Order.
Create a Customer
Click the Add button in the top navigation bar
Click the Add Customer button on the All Customers page
Select the appropriate workgroup in the left navigation pane and click All Customers.
Click Add Customer.
Enter the new customer’s information in the Add Customer form. Primary Email Domain and Company Name are required. The rest are optional.
Click Save.
Repeat steps 1 through 4 for each customer you want to add.
Apply Licenses
Select the correct workgroup on the top of the left navigation pane.
Click Customers on the left navigation pane.
Click the customer that employs the user to whom you want to use the User Migration Bundle license.
Click the Users tab at the top of the page.
Apply the license to the users by checking the box to the left of their emails.
Click the Apply User Migration Bundle License button at the top of the page.
Click Confirm if at least one unassigned User Migration Bundle license is available for each selected user.
Limitations
We recommend completing this migration with multiple migration passes as instructed in the MigrationWiz steps, as this will cause the least impact on the users.
The maximum file size for migration through MigrationWiz varies by migration type and environment, but may never exceed 60GB.
For this migration type, the mailboxes in the Exchange Online tenant must be enabled for Exchange Web Services (EWS).
App password usage, MFA/2FA, and ADFS are not supported for the migration admin account/service account being used by this endpoint.
Migrated Items
Please find below to check the migrated and non-migrated items. We are constantly working to create a better migration experience for you so these items may change over time.
Which items are migrated?
Inbox
Folders
Email
Contacts
Calendars
Tasks
Journals
Notes
Post (when the destination is Exchange or Office 365)
Server-Side mailbox rules
Automatic Replies (Out of Office Messages)
Personal Folder Permissions
Which items are not migrated?
Calendar acceptance status emails
Safe Sender/Block Lists
Prepare the Source Environment
Modern Authentication Requirements
The steps listed in the Required Permission for Performing M365 Mailbox and Archive Migrations article apply to both the source and destination tenant when they are Exchange Online, in regards to Exchange Web Services (EWS) in the mailbox, and archive mailbox. Use a Global Administrator for the configuration steps.
Please review the documentation before preparing the source.
Create an Administrator Account
Create an administrator account in Microsoft 365 to be used for migration or use the global admin account for the tenant. The administrator account must have full access to the user mailboxes, have the required API Permissions, or be granted impersonation rights.
We recommend adding the necessary API permissions to the Modern Authentication app you are using for your O365 mailbox or archive mailbox endpoint. You can follow the steps outlined in this guide, as this is BitTitan's recommended approach.
However, you can still use the BitTitan impersonation approach if you already have a service account with the Application Impersonation role already assigned. Microsoft is phasing out RBAC Application Impersonation in Exchange Online and no longer allows the assignment of this role to new accounts.
Export the User List to a CSV File
This can be used when bulk-adding users to your MigrationWiz project later. You can copy and paste the user list into the Source and Destination Email columns within your MigrationWiz project dashboard under Add > Bulk Add.
To export the user list:
Go to the Microsoft 365 admin portal.
Click Users.
Click Active Users.
Click Export.
Click Continue.
Be sure to save the CSV somewhere you can access it for upload later in the migration.
Prepare the Destination Environment
Modern Authentication Requirements
The steps listed in the Required Permission for Performing M365 Mailbox and Archive Migrations article apply to both the source and destination tenant when they are Exchange Online, in regards to Exchange Web Services (EWS) in the mailbox, and archive mailbox. Use a Global Administrator for the configuration steps.
Please review the documentation before preparing the source.
Set Up User Accounts
Set up user accounts on the destination Office 365 tenant and assign licenses. These can be created in several ways. (The following links are to external articles.)
Create an Administrator Account
Create an administrator account in Microsoft 365 to be used for migration or use the global admin account for the tenant. The administrator account must have full access to the user mailboxes, have the required API Permissions, or be granted impersonation rights.
We recommend adding the necessary API permissions to the Modern Authentication app you are using for your O365 mailbox or archive mailbox endpoint. You can follow the steps outlined in this guide, as this is BitTitan's recommended approach.
However, you can still use the BitTitan impersonation approach if you already have a service account with the Application Impersonation role already assigned. Microsoft is phasing out RBAC Application Impersonation in Exchange Online and no longer allows the assignment of this role to new accounts.
Test Administrator Access
Test that the administrator can access the user mailboxes. Test access to the tenantname.onmicrosoft.com addresses, not to the domainname.com addresses. Make sure that the tenantname.onmicrosoft.com account is attached to each mailbox in Microsoft 365. By default, it should be attached, but if not, it will need to be added as an alias to each account. This can be done through the Microsoft 365 admin portal or via PowerShell scripts.
MigrationWiz Steps
Create a Mailbox Migration project
Click the Go to My Projects button.
Click the Create Project button.
Create a Mailbox project.
Click Next Step.
Enter a Project name and select a Customer.
Click Next Step.
Select endpoints or follow the steps below to create new ones.
Click Save and Go to Summary.
Endpoints
Endpoints are created through MigrationWiz. If you select an existing endpoint from the dropdown, it will only show ten endpoints. If you have more than ten, you may need to search it.
Consider that endpoint search is case and character-specific. For example, Cust0mer will not show up if the search is customer. We recommend keeping a list of endpoints you have created, along with any unique spellings or capitalization you may have used.
Source Endpoints
Click SOURCE SETTINGS.
Click New.
Name the endpoint. It is recommended that the endpoint's name be unique for the project.
Under Endpoint Type, select Microsoft 365 from the dropdown menu. This also applies to the GoDaddy endpoint.
Enter the administrator username and password in the proper fields. This should be the global admin or the admin created in the Prepare the Source section.
Click Add.
Complete the Application (client) ID, the Directory (tenant) ID, and the Client Secret fields.
Click Next Step.
Destination Endpoints
Click DESTINATION SETTINGS.
Click New.
Under Endpoint Type, select Microsoft 365.
Enter the administrator username and password in the proper fields.
Click Add Endpoint.
Complete the Application (client) ID, the Directory (tenant) ID, the Client Secret, and the Region of Destination Tenant fields.
Click Next Step.
Application (client) ID, Directory (tenant) ID, and Client Secret
For Microsoft 365 Mailbox and Archive migrations, MigrationWiz adds the Application (client) ID, Directory (tenant) ID, and Client Secret fields.
While the Application (client) ID and the Directory (tenant) ID are mandatory, the Client Secret field is not. It will depend on the permissions of the user account that performs the migration. Please review the following information before the creation of your M365 endpoints.
The client secret value is not mandatory if you use delegated permissions. Please leave the Client Secret field empty.
The client secret value is mandatory if you use the Application Impersonation using the API Permissions approach.
If you already have an admin account with the Impersonation role enabled (not using the Application Impersonation using API Permissions approach) the client secret value is not mandatory. Please leave the Client Secret field empty.
For more information about how to get the Application (client) ID and Directory (tenant) ID values from the Application Registration, please review step 3 of this article.
Region of Destination Tenant
The Region of Destination Tenant feature optimizes the migration performance and speed by choosing the region closest to the destination tenant. MigrationWiz displays a dropdown that allows you to select the destination region when configuring your destination endpoint.
Endpoint Validation
Once the information has been provided for both, the source and destination endpoint, and the customer selects Save and Go to Summary, MigrationWiz performs an endpoint validation check.
This validation tests the administrator credentials entered into the project and the Modern Authentication setup only. If there is an issue, the screen redirects to the endpoint and provides an error message or flyout that can be selected for more information regarding the error.
Common Errors when Configuring Your Endpoint
For more information on the AADSTS700016, AADSTS90002, and ADDSTS50126 issues review the Common Errors Using Modern Authentication page.
Add Users
Add the user accounts that will be migrated to the project. This may be done in several ways, depending on the size of the project. Steps for each option are in the accordion below, simply click to show the option you select and follow the guidance there.
Default Options for Microsoft 365 Endpoints
By default, some fields are view-only. In other words, you cannot edit or remove them from the support options page. To edit them, you need to edit the source or destination endpoint of your project.
Among these default options, you can find ModernAuthClientIdExport, ModernAuthTenantIdExport, ModernAuthClientSecretExport, ModernAuthClientIdImport, ModernAuthTenantIdImport, and ModernAuthClientSecretImport.
The support options above are required when configuring your endpoint.
Source/Destination Tab
Use impersonation at the Source and Destination. To do so, verify that the Use Impersonation to Authenticate box is check-marked for both, source and destination.
Run Verify Credentials
You may verify the credentials of items in MigrationWiz without migrating data or consuming any licenses.
Open the Project containing items you wish to validate.
Select the items you wish to validate.
Click the Start button in your dashboard.
Select Verify Credentials from the drop-down list.
Once complete, the results of the verification will be shown in the Status section.
Run a Pre-Stage migration pass
Select the users.
Click the Start button from the top.
Select Pre-Stage Migration.
Uncheck the box named Automatic Replies (This option will be removed from the Pre-Stage pass at a later date)
Under the Migration Scheduling section, from the drop-down list, select 90 days ago.
Click Start Migration.
The 90 days is a suggestion, you can select any option you prefer. The Pre-Stage migration will migrate only older mail items. This can be run multiple times with different timeframes selected to migrate data in smaller chunks.
Remove Domain from Source
This should only be done after the Pre-Stage migration pass has been completed. Typically, it is done late on a Friday night. If you need instructions for removing a domain, refer to this document from Microsoft: Remove a domain from Office 365.
If there are several domains in the Source tenant being moved to the new tenant, all of them need to be removed.
In the admin portal, change the UPN of the admin account to the onmicrosoft.com address.
After domain removal, users will not be able to access their email, unless they know and log in with their tenantname.onmicrosoft.com email addresses.
After removal, wait 30 minutes for domain removal replication to complete.
Notify Users
Send an email to the users to let them know what to expect for their Outlook profile reconfiguration. If using DeploymentPro, you can use the DeploymentPro Guide now to set up the users on the destination for Outlook profile configuration.
Verify Domain at Destination
These actions are performed from within the Tenant 2 (Destination) admin portal.
Verify the domain in the Destination Microsoft 365 account. We recommend the use of the wizard in Microsoft 365 for this since once the domain is verified with the Text record, it offers to change all the users to the new Default Domain.
Since the domain was previously added to the account, all that needs to be done is to click the Verify button. If the domain is unable to be verified, and there is an error saying the domain already exists on another account, contact Microsoft Support at 1-800-642-7676 (US Toll-Free, other numbers are also available), and tell them that the domain needs to be manually de-provisioned from Forefront, also known as Exchange Online Protection or EOP.
Confirm that every user has the Destinationdomain.com domain name added to their mailbox.
Download the add_new_domain.ps1 PowerShell script to check for this and add the domain name. This is only necessary if the users do not have the new default domain added to their account.
MX Record Cutover
On the DNS provider's portal, change the primary MX record to reflect the DNS settings for the new Microsoft 365 organization. DNS settings to change include Autodiscover, MX, and SPF records. Also, remove the old settings for Tenant 1. These settings can be found in the Microsoft 365 admin portal, by following these steps:
Inside Microsoft 365, click Admin in the header.
On the Admin page, click Domains in the left pane.
Click the domain name to be set up, and then click the DNS Settings This page lists the DNS records necessary to use the Microsoft 365 services.
Full (Delta) pass
Select the users.
Click the Start button from the top.
Select Full Migration. IMPORTANT: It is recommended to only migrate Automatic Replies in the last migration pass for the user.
Click Start Migration. This migration will be completed quickly since most data is migrated during the Pre-Stage migration; Microsoft 365 to Microsoft 365 migrations have high bandwidth available.
Look through the user list and click any red "failed migration" errors. Review the information and act accordingly.
Run Retry Errors
Each error logged represents an item that was not migrated. MigrationWiz contains a mode in which you can resubmit the migration to retry failed items. This mode of operation is always free of charge. You may only submit mailboxes in this mode only if they satisfy all of the following conditions:
The last migration was completed successfully.
The mailbox contains at least one error.
If your mailbox does not satisfy these conditions, you will receive a warning when submitting the migration in this mode and your request will not be fulfilled.
To submit one or more mailboxes in retry mode, perform the following steps:
Click the Go To My Projects button.
Select the project that contains the mailboxes that you want to retry.
Select the mailboxes that have migration errors.
Click on the Start button.
Select Retry Errors from the menu.
Click the Retry Errors button.
When errors are repaired, they will disappear from the error log. Some errors may not disappear if the Source item was not reprocessed (due to filters, for example), was not deleted or moved, or if the item failed again.
If problems persist, contact Support.
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