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.

App password usage and MFA/2FA are not supported for the admin account being used by this endpoint. 

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.



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.

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.

Exchange Web Services (EWS) must be enabled for the mailboxes in the Exchange Online tenant for this migration type

What items are and are not migrated?


  • Inbox
  • Folders
  • Email
  • Contacts
  • Calendars
  • Tasks
  • Journals
  • Notes
  • Server-Side Rules
  • Folder Permissions
  • Post (when the destination is Exchange or Office 365)
  • Calendar acceptance status emails

Resource Mailboxes

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 is owned by a user. For those cases, 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 it can be accessed by other users.​​​

Not Migrated

  • Safe Sender/Block Lists

Modern Authentication Requirements

Exchange Online EWS Modern Authentication Requirements (click on this box to expand required steps)

The steps listed below apply to both the source and/or 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.


For setup steps that include images, see under Enabling Modern Authentication for EWS between MigrationWiz and your Exchange Online Tenant in the following KB: Authentication Methods for Microsoft 365 (All Products) Migrations

Important: Failure to perform the steps for your Microsoft 365 endpoints, can result in failed jobs with 401 errors like the following in your project: Http POST request to '' failed - 401 Unauthorized

The administrator account being used for the project needs to be excluded from any MFA/2FA policies or Conditional Access policies that can block access for the administrator account. This requirement does not apply to the items or users being migrated in the project.

Configuring Modern Authentication to work with MigrationWiz for mailbox, archive mailbox, and public folder projects in Exchange Online is now the default method after Microsoft discontinued support for Basic Authentication in Exchange Online after 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 Azure Security Defaults must also be disabled in the tenant. (This is often enabled by default for all new Exchange Online tenants and there is no workaround for this requirement). For steps on where to enable/disable the Azure Security Defaults, see Enabling security defaults in the following Microsoft documentation. To disable, set Enable Security defaults to No: Security defaults in Azure AD

Modern Authentication Steps
  • Log in to the Azure AD admin console with a Global Administrator login.
  • Select Azure Active Directory in the Azure Active Directory Admin Center.
  • Select App Registrations, which is found under Manage.
  • Select New Registration at the top of the screen.
  • Give the app a distinct name. You can change this later if necessary.
  • Select the Accounts in any organizational directory button.
  • Under Redirect Uri, select Public Client (mobile & desktop) and set it to urn:ietf:wg:oauth:2.0:oob
  • Click Register.
  • Go back to App registrations.
  • Select the App you just created.
  • In the Overview, you will find a ClientId (aka Application) and Directory (Tenant) ID.
  • Copy both of these to another application, such as Notepad, for use later in this process.
  • Under the Manage menu, select Authentication.
  • Set the option Allow public client flows to Yes
  • Click Save.
  • From the Manage menu, select API permissions.
  • If API permission named User.Read under Microsoft Graph is already present, this can be removed. The Microsoft Graph API is not applicable to this project type and is not used.
  • Select Add a Permission.
  • Select APIs my organization uses

  • Scroll down and select Office 365 Exchange Online

  • Then select Delegated Permissions

  • Select EWS

  • Check the box under EWS for EWS.AccessAsUser.All.
  • Click Add permissions. This permission only allows the OAuth application (MigrationWiz) to be associated with EWS.
      • Important: This does not grant access to all mailbox data.
  • Click Grant admin consent.
  • Click Yes to confirm the settings.
  • In MigrationWiz, select the project that needs to be configured for Modern Authentication.
  • Click the Edit Project menu.
  • Select Advanced Options.
  • Under Support Options enter the ClientID and TenantID information you saved earlier in the following format:
    • If enabling Modern Authentication for the Source:
      • ModernAuthClientIdExport=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
      • ModernAuthTenantIdExport=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
    • If enabling Modern Authentication for the Destination:
      • ModernAuthClientIdImport=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
      • ModernAuthTenantIdImport=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx 
        • Enter the specific ClientID and TenantID for your tenant in place of the xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.
        • These options can be entered for either the Source or the Destination, or both, depending on the settings on the tenants.
        • These options need to be configured for each MigrationWiz project that needs to have Modern Authentication enabled.

  • Run a Verify Credentials to confirm that MigrationWiz can connect using Modern Authentication. 
  • Click on the item that was verified. There will be a message in the MigrationWiz Migration Information page that Modern Authentication is being used. This message will show in the “Migration Errors” box; however, it is not an error. This is just a message confirming that Modern Authentication is now active and being used for the connection.

Prepare 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 either full access to the user mailboxes or be granted impersonation rights. We recommend using impersonation as it will help reduce the likelihood of the migration being throttled by Microsoft. 

To manually set impersonation:

  • Use admin credentials at the Destination.
  • Sign in to the MigrationWiz account.​
  • Edit the Project and click on Advanced Options.
  • If migrating from Microsoft 365, under Source, check Use impersonation to authenticate.
  • If migrating to Microsoft 365, under Destination, check Use impersonation to authenticate.
  • Click on Save Options.

Important: When impersonation is enabled and a job is requested to be performed in the project, MigrationWiz will attempt to run a remote PowerShell command in the tenant to grant the Application Impersonation role to the admin account being used in the project. In order for this to be successful, the admin account in the project needs to be a global admin to have the required permissions to do so.

Microsoft 365 does not always respond in a timely manner for this process and can sometimes cause the job to fail in the project with an error regarding not having permission to impersonate the user being migrated.

If that is the case or the admin account being used in the project is not a global admin, then manually perform this task in the tenant using the steps outlined under Manually Grant Application Impersonation below (you may opt to proactively perform these steps ahead of time instead of having MigrationWiz do it)

Manually Grant Application Impersonation

Note: The remote PowerShell commands below can take several minutes to complete.

  1. Make sure you are using a global admin account to perform these steps
  2. Click the Windows Start button.
  3. Search for Windows PowerShell (PowerShell should already be installed).
  4. Start PowerShell under an administrator context (right-click -> run as administrator).
  5. Run the following PowerShell commands one at a time:
    Set-ExecutionPolicy Unrestricted$LiveCred = Get-Credential

    Install-Module -Name ExchangeOnlineManagement
    Import-Module -Name ExchangeOnlineManagement
    Connect-ExchangeOnline -ConnectionUri -Credential $LiveCred


    The Enable command may take a long time to run and may error out. If so, wait a few minutes and run it again.
    New-ManagementRoleAssignment -Role "ApplicationImpersonation" -User
  • Make sure to replace "" in the PowerShell command above with the admin account being used for migration.
  • Ignore any errors such as "This operation is not available in current service offer."
  • Ignore any errors such as "The assignment of the management role 'ApplicationImpersonation' [...] won't take effect until user is migrated."
  • If connecting to GCC High with powershell, use Connect-ExchangeOnline -ConnectionUri -Credential $LiveCred -ExchangeEnvironmentName O365USGovGCCHigh



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

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 either full access to the user mailboxes or be granted impersonation rights. We recommend using impersonation as it will help reduce the likelihood of the migration being throttled by Microsoft. For specific steps to set impersonation manually, follow the steps under Manually Grant Application Impersonation in the Prepare the Source section of this guide and apply them to the Destination tenant.


Test Administrator Access

Test that the administrator can access user mailboxes. Test access to the addresses, not to the addresses. Make sure that the 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. For mailbox migrations, use administrative credentials to access mailboxes. In most migration scenarios, the admin account needs to 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 a Source Endpoint from the Endpoint dropdown menu or create a new one following the steps below.
  8. Select a Destination Endpoint from the Endpoint dropdown menu or create a new one following the steps below.
  9. Click Save and Go to Summary.

Mailbox Migration Settings: Every setting on the project is applied to all mailboxes associated with that project. For settings that are represented as checkboxes, only selected settings are applied to the project. Not selecting a checkbox does not disable a selected setting inherited from the project.


Endpoints are now created through MigrationWiz, rather than through MSPComplete. The steps for this section outline how to create the endpoints in MigrationWiz.

If you are selecting an existing endpoint, keep in mind that only ten endpoints will show in the drop-down. If you have more than ten, you may need to search. 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.

You may either use existing endpoints (if one for this migration scenario already exists) or create new ones.

To create a new endpoint: (Perform these steps for both the source and destination endpoints)

  1. Click New.
  2. Name the endpoint (It is highly recommended to create a unique name for your source and destination endpoints) 
  3. Under Endpoint Type, select the endpoint from the options below that corresponds with the type of Microsoft 365 tenant being used:
  • Microsoft 365 - (This is also used for hosted GoDaddy O365 and GCC Commercial tenants)
  • Microsoft 365 (China)
  • Microsoft 365 (Germany)
  • Microsoft 365 (US Government) - (Use this for GCC High tenants only)
  • Enter the administrator username and password in the fields. This should be the global admin or the admin created in the Prepare the Source section. 
  • Click Add. 
  • Click Next Step.

Add Users


If the domain name is being migrated to the new destination tenant, it is strongly recommended that users in the migration project be migrated using the domain names for both the source and destination email addresses, rather than using the vanity domain.

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 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. The steps for this are below. 

Larger Migrations:

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

Autodiscover will add all users (including shared mailboxes) found on the source tenant. This can then be edited in the project to remove users not being migrated. All users will be 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. The source administrator account must have an active mailbox in the source tenant to use Autodiscover.

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.

Quick Add
This option allows you to add items one at a time. You have to enter an email address, login name, and password for each user if you didn't enter administrative credentials when setting up the project. You only have to provide an email address if you entered administrative credentials when setting up the project.
Bulk Add

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.

​The Autodiscover process within MigrationWiz can be used to discover items from the Source environment so that they can be imported into your projects. 

There are a few requirements in order 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.

Note: 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, autodiscover 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.

Set the Project Advanced Options

The following options are most valuable for this migration scenario:

Set to use impersonation at the Source. Checkmark the Use impersonation at Source box.

Set to use impersonation at the Destination. Checkmark the Use impersonation at Destination box.

Under Support/Support Options:


The RecipientMapping above is just an example; do not copy this verbatim. It needs to be changed to reflect the account name and the customer destination domain name.

This is a very important step for Microsoft 365 to Microsoft 365 migrations. It ensures that emails have the ability to 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 account name (which will no longer be available, once the tenant is retired).

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 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.

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

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.​ 


Purchase and apply User Migration Bundle licenses for all the users being migrated. For this migration type, we suggest the User Migration Bundle.

  • 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.

Purchasing Licenses

  1. Sign in to your BitTitan account. 
  2. In the top navigation bar, click Purchase.
  3. Click the Select button and choose the license type you need.
  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.

Applying User Migration Bundle Licenses

  1. Sign in to MigrationWiz at
    • You can either sign in and make sure to select the MigrationWiz button above the email field or sign into MSPComplete page, then click the All Products button and select MigrationWiz.
  2. Select the correct workgroup on the top of the left navigation pane.
    Note: This is the workgroup that the customer and migration project were created under. Your account must be part of the workgroup and project sharing must be enabled, if the project was not created under your account. For more information see Add and Edit Workgroups and Project Sharing in MigrationWiz.
  3. Click the project that requires licenses to be applied.
    • Ensure that the UMB licenses are applied towards the UPN/SMTP based on vanity domain. Subsequently use the change domain to update the line items to point to address.
  4. Check the box to the left of the email for the user(s) to whom you want to apply a User Migration Bundle license.
  5. Click the More menu (3 stacked lines) at the top of the project page.
  6. Click Apply User Migration Bundle License.

If you have more questions about licensing, including redeeming coupons, or changing categories, see MigrationWiz Licenses.

Run a Pre-Stage migration pass

  1. Select the users.
  2. Click the Start button from the top.
  3. select Pre-Stage Migration.
  4. Under the Migration Scheduling section, from the drop-down list, select 90 days ago.
  5. 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 address.

After domain removal, users will not be able to access their email, unless they know and log in with their 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 deprovisioned from Forefront, also known as Exchange Online Protection or EOP.
  2. Confirm that every user has the 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 set in order 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.
  4. Click Start Migration. This migration will complete 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 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), has been deleted or moved, or if the item failed again. 

If problems persist, contact Support


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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