1. BitTitan Help Center
  2. Perform a Migration
  3. Microsoft 365 Migrations
  4. Microsoft Exchange Online/Office 365 Mailbox Migrations

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. 

This guide does not include steps for when using Coexistence during the migration. For the migration strategy guide when using Coexistence, see Exchange Online (Microsoft 365) to Exchange Online (Microsoft 365) - Migration Guide - Using Coexistence - Different Domain.

MigrationWiz

MigrationWiz is not a sync tool. Already migrated items 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:

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

Purchase licenses by following the steps below:

  1. Sign in to your BitTitan account. 
  2. In the top navigation bar, click Purchase.
  3. Click the Select button and choose User Migration Bundle licenses.
  4. Enter the number of licenses you want to purchase. Click Buy Now.
  5. Enter a Billing address if applicable.
  6. Click Next.
  7. Review the Order Summary and enter a payment method.
  8. Click Place Your Order.

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.

Warning

MigrationWiz no longer supports Team's 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.

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) 

    Important

    Only Automatic Replies should be migrated in the last migration pass for the user. 
  • Personal Folder Permissions

Resource Mailbox

We handle resource mailboxes the same way that we handle regular user mailboxes. If you can log in to the resource mailbox using a web client (i.e., Outlook Web Access), we should be able to log in as well and migrate the data. If there is no way to log in to the resource mailbox using a web client (like OWA), then we also cannot log in and migrate the data.

In some cases, the resource mailbox is just a shared calendar that a user owns. When the user's mailbox is migrated, we should be able to migrate the resource mailbox calendar as one of the user's calendars. Once the migration is complete, you could set sharing/permissions on the calendar so that other users can access it.​​​

Which items are not migrated?
  • Calendar acceptance status emails
  • Safe Sender/Block Lists

For additional features and limitations visit MigrationWiz: Migrated and Not Migrated Items.

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:

  1. Go to the Microsoft 365 admin portal.
  2. Click Users.
  3. Click Active Users.
  4. Click Export.
  5. 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

  1. Click the Go to My Projects button.
  2. Click the Create Project button.
  3. Create a Mailbox project.

    Important

    For mailbox migrations, use admin credentials to access mailboxes. In most migration scenarios, the admin account must have full access rights to the Source mailboxes.

  4. Click Next Step.
  5. Enter a Project name and select a Customer.
  6. Click Next Step.
  7. Select endpoints or follow the steps below to create new ones.
  8. Click Save and Go to Summary.

Mailbox Migration Settings

Every setting on the project is applied to all mailboxes associated with that project. Only selected settings represented as checkboxes are applied to the project. Not selecting a checkbox does not disable a selected setting inherited from the project.

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.

Source Endpoint Destination Endpoint

Create your source endpoint by following the next steps:

  1. Click SOURCE SETTINGS.
  2. Click New.
  3. Name the endpoint. It is recommended that the endpoint's name be unique for the project.
  4. Under Endpoint Type, select Microsoft 365 from the dropdown menu. This also applies to the GoDaddy endpoint.
  5. 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. 
  6. Click Add.

  7. Complete the Application (client) ID, the Directory (tenant) ID, and the Client Secret fields.

    Source Settings.png

  8. 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.

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

MigrationWiz displays a dropdown to select the Preferred Region of the Tenant at the destination endpoint. This value updates the Preferred Region of the Destination Tenant field in the project's Advanced Options, and vice versa. You will notice that both values are always the same.

The Region of Destination Tenant feature optimizes the migration performance and speed when choosing the region closest to the destination tenant.

Tip

You can find the region of your destination tenant directly in the Microsoft Entra admin center by going to Identity > Overview > Properties, and using the Country or region or the Data location.

Country or region.png

For more information on this topic, review this article.

Warning

If you do not complete this field you will not be able to save your project and the “This field cannot be left blank.” error will appear.

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

Important

We suggest using .onmicrosoft.com domain names for both the source and destination email addresses instead of the custom domain if you are migrating the domain name to a new destination tenant.

To do this, you'll add the users using their Vanity Domain and once they're in the project, select all the users and click the Change Domains option in the menu to bulk change them to using the .onmicrosoft.com domain. 

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. You can find the steps for this type of migration, below.

Quick Add
This option allows you to add items one at a time. To do so, you only have to provide an email address if you entered administrative credentials when setting up the project. If you did not, enter the following user information:
  • An email address
  • Login name
  • Password
  • Mailbox status

Larger Migrations

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

Bulk Add

Bulk Add uses a CSV containing the source and destination email addresses for the users to add the users to the project. If migrating only a specific group from a tenant, we recommend using the Bulk Add option.

MigrationWiz allows you to bulk import mailboxes into the system.

To import one or more mailboxes:

  1. Sign in to your MigrationWiz account.
  2. Select the Project for which you want to perform the bulk import.
  3. Click Add.
  4. Click Bulk Add. 
  5. Follow the instructions on the page.

    Important

    After adding new users to the Bulk Add Items page, make sure to select the radio button All newly detected mailboxes will be migrated as shown below before clicking on the green Save button)

    New Bulk Add Requirement.png

Autodiscover

​Autodiscover process within MigrationWiz can be used to discover items from the Source environment so that they can be imported into your projects. This can then be edited in the project to remove users not being migrated. All users are added with the source and destination email addresses set to match the source email.

This can be changed by using the Change Domain Name button at the top of the project page. If the usernames are changing during the migration, we recommend using the Bulk Add option.

There are a few requirements for this to work:

  • The Source has to be Exchange 2007 or later, or Microsoft 365, or G Suite. If you are using Autodiscover from G Suite, all G Suite domains must be added to the list of domains in the Endpoint.
    • G Suite does not support Autodiscover when mailbox addresses are imported into MigrationWiz line items.
  • The endpoint on the Source needs to use admin credentials.
  • For mailbox migration projects, the admin account that is specified within the Source endpoint needs to have a mailbox associated with it.
  • The admin mailbox must be listed in the public Global Address List (GAL).
  • The migration project type needs to be a Mailbox migration. For the exact steps to be followed during your migration, refer to the relevant Migration Guide. All Migration Guides can be found on the Help Center site.

Important

One additional item to note here is that there is no way to restrict the IP addresses that the connection will come from.  This means that the steps outlined in our IP Lockdown guide will not apply here.  If your environment requires that any IP addresses be whitelisted, it is recommended that items be added to your project using one of the other available options.

Autodiscover of items will not work while using Modern Authentication

Autodiscover exposes the following items:

  • For mailbox migration, auto-discover will list all mailboxes at the Source.

Steps to Run Autodiscover

  1. Navigate to the project you want to import users into.

  2. Ensure that you have created an endpoint for the source project.

  3. Once in the project, on the top navigation bar, click on the Add drop-down, then select Autodiscover Items. This will begin the Autodiscover process.

  4. Once discovered, click on the Import button, to import the items into your MigrationWiz project.

Advanced Options

Support Tab

  • RecipientMapping="@sourcetenantname.onmicrosoft.com->@destinationdomainname.com" RecipientMappings ensures that emails can be replied to, even after the Full (Delta) migration has occurred because they will be mapped to the new destination domain name, rather than using the old sourcetenantname.onmicrosoft.com account name (which will no longer be available, once the tenant is retired).

    • If the domain name is changing, then the source vanity domain can be used in the RecipientMapping as in this example: RecipientMapping="@sourcedomainname->@destinationdomainname"
      More than one mapping expression can be used as long as the destination domain remains the same in the RecipientMapping.

    • If the User Prefix is changing, follow the instructions here, User Prefix Changes.

      Important

      This is a very important step for Microsoft 365 to Microsoft 365 migrations. The RecipientMapping above is just an example. Do not copy this verbatim. It needs to be changed to reflect the sourcetenantname.onmicrosoft.com account name and the customer destination domain name.

Recipient Mappings

Recipient mappings are a useful way to ensure that:

  • All email remains replyable to, post-migration, even after a Full (Delta) Migration has occurred when performing a tenant-to-tenant migration while keeping the same domain name; or when changing domain names from Source to Destination.
  • Calendar ownership and display name match on the destination when performing a tenant-to-tenant migration, while keeping the same domain name; or when changing domain names from Source to Destination.

If you are using recipient mapping while migrating from one Source domain to multiple Destination domains, a project is required for each Destination domain.

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.

Important

Keep in mind that the ModernAuthClientSecretExport and the ModernAuthClientSecretImport support options are text-masked.

Warning

You cannot update the default Advanced Options, in case you try to modify or add new ones the following message arises.
Duplicate Support Option.png

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.

  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.​ 

Run a Pre-Stage migration pass

  1. Select the users.
  2. Click the Start button from the top.
  3. Select Pre-Stage Migration.
  4. Uncheck the box named Automatic Replies (This option will be removed from the Pre-Stage pass at a later date)
  5. Under the Migration Scheduling section, from the drop-down list, select 90 days ago.
  6. 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.

  1. 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.
  2. Confirm that every user has the Destinationdomain.com domain name added to their mailbox.
  3.  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:

  1. Inside Microsoft 365, click Admin in the header.
  2. On the Admin page, click Domains in the left pane.
  3. 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

  1. Select the users.
  2. Click the Start button from the top.
  3. Select Full Migration. IMPORTANT: It is recommended to only migrate Automatic Replies in the last migration pass for the user. 
  4. 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.
  5. 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:

  1. The last migration 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. Click the Go To My Projects button.
  2. Select the project that contains the mailboxes that you want to retry.
  3. Select the mailboxes that have migration errors.
  4. Click on the Start button.
  5. Select Retry Errors from the menu.
  6. 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. 

Post-Migration

If not using DeploymentPro, users must create new Outlook profiles, set up their signatures again, and reattach any PST files that were attached to their previous profile.

Click the bar chart icon in the MigrationWiz dashboard to receive an email containing all the project migration statistics. 

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