This is the complete onboarding task flow for migrating mailboxes from one Microsoft 365 tenant to another Microsoft 365 tenant.

This migration scenario is useful if you want to migrate data from individual mailboxes into shared Microsoft 365 Groups mailboxes. This migration scenario only supports the migration of mail items into the Microsoft 365 Groups.

First time?

This migration guide contains the necessary steps to perform the actual migration, but there are many steps to preparing for migration. 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.

MigrationWiz

MigrationWiz is a migration tool, not a syncing tool. If changes are made at the source after migration, they will not sync to the destination, nor will changes made at the destination sync to the source. We do not have “live” monitoring of changes (as with a sync agent) and we cannot handle scenarios such as conflict resolution without user interaction.

Prerequisites

It is important to highlight and meet the following prerequisites for a smooth migration project.

• Exchange Web Services (EWS) must be enabled for the mailboxes in the Exchange Online tenant.

Licensing

We recommend that you purchase User Migration Bundle licenses for this migration scenario. User Migration Bundle licenses allow the performance of multiple migrations with a single license. For questions on licensing, visit Which Migration License Do I Need?.

To use your license by following the next steps:

1. Review Considerations.
2. Purchase Licenses.
3. Create a Customer.
4. Apply Licenses.

Limitations

• We are not able to support migrations with two-factor or multifactor authentication. 

• App password usage, MFA/2FA, SSO, and ADFS are not supported for the migration service account being used by this endpoint.

  Warning

  MigrationWiz no longer supports Teams private chat history as part of Mailbox migrations due to Microsoft's restriction on Teams data access through EWS. For more information please review this article.

Migrated Items

Please click the bars 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.

Prepare the Source Environment

# Check current status:
Get-OrganizationConfig | fl EWSEnabled 
# Enable EWS: 
Set-OrganizationConfig -EWSEnabled $true

# Check a specific mailbox 
Get-CASMailbox -Identity user@domain.com | fl EWSEnabled 
# Enable EWS for a specific mailbox 
Set-CASMailbox -Identity user@domain.com -EWSEnabled $true 
# Enable EWS for ALL mailboxes (use with caution) 
Get-CASMailbox -ResultSize Unlimited | Set-CASMailbox -EWSEnabled $true

Get-OrganizationConfig -RetrieveEwsOperationAccessPolicy | Format-List EwsAllowedAppIDs

Set-OrganizationConfig -EwsAllowedAppIDs "11111111-2222-3333-4444-555555555555,aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee"

Get-OrganizationConfig -RetrieveEwsOperationAccessPolicy | Format-List EwsAllowedAppIDs

# Read the current allow list
$current = (Get-OrganizationConfig -RetrieveEwsOperationAccessPolicy | Select-Object -ExpandProperty EwsAllowedAppIDs)
# Define the new App ID to add
$newAppId = "99999999-8888-7777-6666-555555555555"
# Combine existing and new values
$updated = @($current, $newAppId)
# Write the updated allow list back
Set-OrganizationConfig -EwsAllowedAppIDs ($updated -join ",")

# Read the current allow list
$current = (Get-OrganizationConfig -RetrieveEwsOperationAccessPolicy | Select-Object -ExpandProperty EwsAllowedAppIDs)
# Define the App ID to remove
$removeAppId = "99999999-8888-7777-6666-555555555555"
# Split the comma-separated list into individual App IDs
$appIds = $current -split ","
# Remove the specified App ID
$updated = $appIds | Where-Object { $_ -ne $removeAppId }
# Write the updated allow list back
Set-OrganizationConfig -EwsAllowedAppIDs ($updated -join ",")

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 a Migration Service Account

Create a migration service account in Microsoft 365 for the tenant, this account does not require any admin role assigned. However, it must have full access to the user mailboxes or have the required API Permissions.

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.

Prepare the Destination Environment

# Check current status:
Get-OrganizationConfig | fl EWSEnabled 
# Enable EWS: 
Set-OrganizationConfig -EWSEnabled $true

# Check a specific mailbox 
Get-CASMailbox -Identity user@domain.com | fl EWSEnabled 
# Enable EWS for a specific mailbox 
Set-CASMailbox -Identity user@domain.com -EWSEnabled $true 
# Enable EWS for ALL mailboxes (use with caution) 
Get-CASMailbox -ResultSize Unlimited | Set-CASMailbox -EWSEnabled $true

Get-OrganizationConfig -RetrieveEwsOperationAccessPolicy | Format-List EwsAllowedAppIDs

Set-OrganizationConfig -EwsAllowedAppIDs "11111111-2222-3333-4444-555555555555,aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee"

Get-OrganizationConfig -RetrieveEwsOperationAccessPolicy | Format-List EwsAllowedAppIDs

# Read the current allow list
$current = (Get-OrganizationConfig -RetrieveEwsOperationAccessPolicy | Select-Object -ExpandProperty EwsAllowedAppIDs)
# Define the new App ID to add
$newAppId = "99999999-8888-7777-6666-555555555555"
# Combine existing and new values
$updated = @($current, $newAppId)
# Write the updated allow list back
Set-OrganizationConfig -EwsAllowedAppIDs ($updated -join ",")

# Read the current allow list
$current = (Get-OrganizationConfig -RetrieveEwsOperationAccessPolicy | Select-Object -ExpandProperty EwsAllowedAppIDs)
# Define the App ID to remove
$removeAppId = "99999999-8888-7777-6666-555555555555"
# Split the comma-separated list into individual App IDs
$appIds = $current -split ","
# Remove the specified App ID
$updated = $appIds | Where-Object { $_ -ne $removeAppId }
# Write the updated allow list back
Set-OrganizationConfig -EwsAllowedAppIDs ($updated -join ",")

Modern Authentication Requirements

The steps listed in Authentication Methods for Microsoft 365 (All Products) Migrations apply to both the source and destination tenant when they are Exchange Online, in regards to Exchange Web Services (EWS) in mailbox, archive mailbox, and public folder projects. Use a Global Administrator for the configuration steps.

Please review the documentation before preparing the destination.

Create a Migration Service Account

Create a migration service account in Microsoft 365 for the tenant, this account does not require any admin role assigned. However, it must have full access to the user mailboxes or have the required API Permissions.

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.

Create the Microsoft 365 Groups

This step is only necessary if the group does not already exist. Either of these options can create Microsoft 365 Groups:

• Opening Outlook Web Access / Outlook On The Web. 
• Via PowerShell, using the New-UnifiedGroup command. 
• Created in the Microsoft 365 admin portal. 

Manage Group Membership

The following actions may be performed to manage group membership before migration.

• Add members to the Group using the Microsoft 365 admin center.
• Add the migration service account as a member of the group.
• Add the migration service account as an owner of the group.

MigrationWiz Steps

Create the Mailbox Migration Project

You will now create the migration project and add your users.

Once a project is set up, you cannot add more users or make changes to the configuration except for advanced options. If you want to add users to the organization, please add them to the source before creating the project or add them manually to the destination. Once the project is created, users will be added to the project automatically from the source endpoint.

1. Click the Go To My Projects button.
2. Click the Create Project button.
3. Create a Mailbox migration. 
4. Click Next Step.
5.  

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.

Create your Endpoints

Please review the following tabs to create your destination and source endpoints.

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.

Please review the following information before the creation of your M365 endpoints.

• The client secret value is mandatory if you using the API Permissions approach.
• If you already have a migration service account with M365 Exchange delegation permissions to the migrating mailboxes with the permissions: 
  • Read and manage (Full Access).
  • Send on behalf.
    
     

  • You can uncheck “Impersonation to Authenticate” under Edit > Advanced Options > Source / Destination.
    This approach is best suited for a 'One-to-Few' migration scenario, as Exchange Delegations must be enabled individually for each mailbox.

    Warning

    Keep in mind that Microsoft has started removing the application impersonation role from O365, meaning there is no telling when that will eventually fail. It is highly recommended that you switch to the API Permissions approach.

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 migration performance and speed by identifying the region closest to the destination tenant (continent-level). For Microsoft 365 endpoints, MigrationWiz detects and selects the appropriate region automatically once you create and save your project.

Please note that each time you edit your project endpoints, the following message will appear at the top of your project window (where XXXX is the detected region):

Automatically detected destination tenant's region and assigned to the 'BitTitan Datacenter' in XXXX.

For this migration type, you cannot manually change the region of the destination tenant. In case you need to modify it, contact our support team.

Project Settings

Once the endpoint configuration is complete, the Project Settings window will open. In this window, you can choose from the following options based on your requirements:

• Skip Modern Auth Credential Validation: By choosing this option you will disable the Modern Auth verification across all endpoints.

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 migration service account 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, review the AADSTS700016, AADSTS90002, and ADDSTS50126 issues on the Common Errors Using Modern Authentication page.

Add User Accounts

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.

Small Migrations

For small migrations, it is easy to add users one at a time using Quick Add. The steps for this are below. 

Larger Migrations

For larger migrations, we recommend either using the Autodiscover or Bulk Add option.

Advanced Options

The following option is the most valuable for this migration scenario.

Support Tab

• InitializationTimeout=8 This increases the initialization timeout window to eight hours. This value is in hours, up to a maximum of 100 hours. Values above 100 are in milliseconds. For example:​
  • InitializationTimeout=2 will increase the timeout to 2 hours.
  • InitializationTimeout=8 will increase the timeout to 8 hours.
  • InitializationTimeout=14400000 will increase the timeout to 4 hours.
  • InitializationTimeout=21600000 will increase the timeout to 6 hours.

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

For now, the new API Permissions approach does require the Use Impersonation to Authenticate box checked for your O365 endpoints along with the Client secret value that you supplied during the Endpoint creation.

Filtering Tab

•  ^(?!Inbox$). This RegEx expression migrates the Inbox, but not its subfolders. To migrate both the Inbox folder and Calendars folder, use instead the RegEx expression ^(?!Inbox$|Calendar$). These filters are used to prevent failures, as Groups should only contain an Inbox folder, and possibly a Calendar.  No other folders are supported. This expression must be in the source language, such as ^(?!Boîte de réception$) for French.

Run Verify Credentials

You may verify the credentials of items in MigrationWiz without migrating data or consuming any licenses.

1. Open the Project containing items you wish to validate.
2. Select the items you wish to validate.
3. Click the Start button in your dashboard.
4. Select Verify Credentials from the drop-down list.

Once complete, the results of the verification will be shown in the Status section.​ 

Notify Users

Notify users that a migration is occurring. Send an email to all users telling them the time and date of the migration.

MX Record Cutover

Change over MX records on the DNS providers' portal. Also, include the AutoDiscover (CName) setting.

Send an email to end users to let them know what to expect for their Outlook profile reconfiguration. 

Run Migration

You are now ready to run the migration. 

1. Select the users.
2. Click the Start button from the top.
3. Select Full Migration.
4. Select to migrate Mail only.
5. Click Start Migration.

Run Retry Errors

Look through the user list and click any red "failed migration" errors. Review the information and act accordingly. 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:

1. The last migration pass was completed successfully.
2. 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:

1. Sign into your MigrationWiz account.
2. Click the Go To My Projects button.
3. Select the project that contains the mailboxes that you want to retry.
4. Select the mailboxes that have migration errors.
5. Click on the Start button.
6. Select Retry Errors from the menu.
7. 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), has been deleted or moved, or if the item failed again. 

If problems persist contact Support.

Post Migration

• Show users how to access the Microsoft 365 Group; this will appear in their Outlook, under Groups.
• Click the pie chart icon in the MigrationWiz dashboard to receive an email containing all the project migration statistics.