G Suite (Gmail API) to Exchange Online (Microsoft 365) Migration Guide

This document will guide you through migrating from G Suite to Exchange Online (Microsoft 365) via the Gmail API endpoint. 


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.

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. If you have never performed a migration before, we suggest reading that before beginning the steps outlined in this scenario.


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


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 MigrationWiz Licenses.

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.


  • App passwords are not supported for the Microsoft 365 endpoint. 
  • The maximum file size for migration through MigrationWiz varies by migration type and environment, but may never exceed 60GB.
  • Some item types are not migrated. Click the bar below to expand the full list of what item types are and are not migrated. We are constantly working to create a better migration experience for you, so these items may change.


  • When migrating from G Suite as a source, contacts in Contact Groups (which look like subfolders of the Contacts folder) will migrate to the top-level contacts folder on the destination. Folders will be created for each group but the contacts will not be sorted into those folders.
  • Calendars can have multiple Owners. An Owner is anyone with "Make changes and manage sharing" permissions, so shared calendars will be migrated to users with these permissions by default.

Migrated Items

Which is the migration mapping?

Keep in mind that relationship fields do not migrate fully from Gmail. The mappings are as follows: 

Google contact field

Mapping in O365



contact body

Description in the body































Organization (primary)


Also stores name, department, title and job descriptions

Organizations (non-primary)


Also stores name, department, title and job descriptions



Only first 3 are stored. Rest are stored in overflow properties.



Only first 3 are stored. Rest are stored in overflow properties.

Phone numbers



  • home
  • home fax
  • mobile
  • pager
  • work
  • work fax
  • other

If any number is already set, we append to overflow contact properties

Postal Addresses

Physical Addresses


  • home

  • work

  • other

If any address is already set, we append to overflow contact properties.

Also stores city, country or region, postal code, state and street


Wedding Anniversary (only for anniversary)

Rest are stored in overflow properties

Relations (value = "assistant")



Relations (value = "child")



Relations (value = "domestic-partner")



Relations (value = "manager")



Relations (value = "partner")



Relations (value = "spouse")



Relations (value = others)

Others stored in overflow properties








User defined fields

All stored in overflow properties


Name.GivenNamePhonetics + Name.AdditionalNamePhonetics

Stored as extended property



Stored as extended property



Stored as extended property



Stored as extended property



Stored as extended property


Which items are migrated?
  • Inbox
  • Folders/Labels
  • Email
  • Muted Email (as regular email)
  • Contacts
  • Calendars (including links for Google Hangouts within calendar meetings)
  • Calendar Notifications
  • Google Categories (i.e., the Google category flags: Social, Promotions, Updates, Forums)

Links for Google Hangouts are a new default feature added to Google Meetings. Microsoft 365 does not have the corresponding property to map. Therefore, when migrating to Microsoft 365, the links for Google Hangouts are added to the beginning of the meeting description body text on Microsoft 365.

With Google API Endpoint at Source

With this endpoint, all items listed above migrate as before. However, utilizing the API endpoint enables migration of the following items as well. The following items are not migrated via the IMAP endpoint. 

  • Google Categories (Category flags, i.e. Social, Promotions, Updates, Forums)
  • Snoozed and Scheduled emails - these are migrated like regular emails to custom destination labels. Their properties are not migrated.
Which items are not migrated?
  • Calendar Reminders
  • Google Spaces
  • Google Spaces Chats
  • Appointments
  • Chat message attachments
  • Google Groups for Business (including forums and collaborative inboxes)
  • Calendar attachments
  • Calendar reminders
  • Tasks
  • Chats and chat history
  • Email attachments that are links to Google Drive
  • Some calendar colors
  • Rules
  • Calendar permissions
  • Automatic replies

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


All color category meta tags are transferred over, but Microsoft 365 does not have direct color mappings from Google G Suite, so certain colors do not get mapped over, thus the colors are not displayed in Microsoft 365 for the calendar entries.

Preparing the Source Environment

The G Suite (Gmail API) source endpoint requires your tenant service account to be set up and Google APIs to be enabled.


  • Subscription to Google Cloud Platform.
  • Google Super Administrator account.
  • Ability to set up a service account on the G Suite tenant.
  • Service account must be set up before the MigrationWiz project is created.
  • All accounts being migrated must be in Active status in the tenant. Users that are set to a status of Inactive will not be able to fully migrate and will fail in the project.

Create a Google Project

  1. Go to the Google Cloud Platform (GCP) Console and sign in as a super administrator. Choose one of the options below:
    • If you haven't used the Google Cloud Platform Console before, agree to the Terms of Service and click Create Project.
    • If you have used the Google Cloud Platform Console before, at the top of the screen next to your most recent project name, click Down to open your projects list. Then, click New Project.
  2. Enter a project name and click Create.

If you are not able to create a project here, it may be that the ability to create projects has been disabled for your tenant. To check this, navigate to the Google Admin Center, click on Apps > Additional Google Services, and select the Google Cloud Platform. Once there, you should see a setting that can be toggled to allow users to create projects.

Enable APIs for Service Account

  1. From the Google Cloud Platform Console, click Menu () > APIs & Services > Library.
  2. Enable the following APIs by selecting the specific API and clicking Enable. Repeat for each API:
    • Google Calendar API
    • Gmail API
    • People API
    • Contacts API
    • Admin SDK

Make sure that the Gmail, Calendar, and Contacts services are enabled within the Google tenant. You can control services for your users by following the instructions on this page: G Suite and Google Services Access.

Create a Customer Tenant Service Account

  1. From the Google Cloud Platform Console, click Menu () > IAM & Admin > Service accounts.
  2. Click Create Service Account and enter a name.
  3. Click Create.
  4. Assign the role of Owner to the new Service Account by selecting Owner from the Role Dropdown menu.
  5. Click Continue.
  6. Click Done.
  7. Click the three dots to the right of the service account and click manage keys then select Manage Keys ->> Add Key ->>Create new key.
  8. Make sure that JSON is selected and click Create.
    • Make sure that you download the key as a JSON file and make a note of the name and location of the file. This JSON file will be used when setting up the migration endpoint in the Mailbox Migration project.
    • The JSON file must contain information in the following fields: “type”, “private key”, and “client email”. If these mandatory fields are empty the file upload during endpoint creation will fail.
  9. Click Close.

Setting the Scopes for the Migration

  1. From the Google Cloud Platform Console, click Menu (Google_Menu.png) > IAM & Admin > Service accounts.
  2. Find the service account that was set up in Step 3.
  3. Find the Unique ID field for that service account and copy the ID number. This is the Client ID number that will be used in a later step.
    • This field often needs to be added to the view. Click on the Column display options button (UniqueID2.png) and add a checkmark to Unique ID, then click OK.
    • This Client ID should be considered similar to Administrator account passwords and handled securely.
  4. Go to the G Suite admin page at admin.google.com click on Security > Advanced Settings > Manage API Client Access.
    If your account shows the latest UI updates from Google, Go to the G Suite admin page at admin.google.com click Security > Access and Data Controls > API Controls.  Scroll down to ‘Domain-wide delegation’, click Manage domain-wide delegation > On the Manage domain-wide delegation page, click Add new.
  6. Click Add New.
  7. In the Client Name field, paste the Unique ID copied above.
  8. Enter one of the following groups of scopes into the OAuth Scopes (comma-delimited) field, depending on whether G Suite is the Source or Destination.
    G Suite as the Source (read-only scopes)
    https://mail.google.com/, https://www.google.com/m8/feeds, https://www.googleapis.com/auth/contacts.readonly, https://www.googleapis.com/auth/calendar, https://www.googleapis.com/auth/calendar.readonly, https://www.googleapis.com/auth/admin.directory.group.readonly, https://www.googleapis.com/auth/admin.directory.user.readonly, https://www.googleapis.com/auth/drive, https://sites.google.com/feeds/, https://www.googleapis.com/auth/gmail.settings.sharing, https://www.googleapis.com/auth/gmail.settings.basic,https://www.googleapis.com/auth/contacts.other.readonly 
  9. Click Authorize.

You should now see your specific Unique ID and the scopes listed, similar to what is shown below:

40520a97-ba80-46f1-ae4b-710e52fe251f.png 2c5866c2-efbb-499f-89a2-e55f36b8f5e7.png

Preparing the Destination Environment

  1. Set up user accounts on the destination Office 365 tenant and assign licenses. These can be created in several ways. We have a few options listed below:
  2. Create an administrator account in Office 365 to be used for migration or use the global admin account for the tenant. The minimal service account requirements are full access rights to the mailbox and impersonation rights. We recommend using impersonation over delegation because it is Exchange Online. For specific steps to set impersonation manually, see Impersonation and Delegation.
  3. Test that the administrator can access 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 Office 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 Office 365 admin portal or via PowerShell scripts. Read the Verify mailbox accessibility using EWS article for more information.

Modern Authentication Requirements


These steps must be performed to complete the endpoint setup in Step 9 under MigrationWiz Steps.

The steps listed in the Obtain Client and Tenant ID Settings for Mailbox and Exchange Online Migrations section of the Authentication Methods Migrations KB 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.

MigrationWiz Steps

Create a Mailbox Migration Project

  1. From the MigrationWiz dashboard, click Go To My Projects.
  2. Click Create Project.
  3. Select a Mailbox migration type. 
  4. Click Next Step.
  5. Enter a project name and select a Customer from the list.
    1. If the customer hasn’t already been created, you can do so here.
    2. To create a new customer, click New, provide required details including primary email domain and company name, and click Save.
  6. Click Next Step.
  7. Select G Suite (Gmail API) endpoint from the source drop-down menu. If an endpoint has not been created, click New.
    1. Enter a name in the Endpoint Name field.
    2. Select G Suite (Gmail API) from the Endpoint Type drop-down menu.
    3. Upload the JSON file for your service account setup.
    4. Provide a valid super administrator email address for the G Suite account that matches the end user domain.
  8. Select the Office 365 destination endpoint from the destination drop-down menu. If an endpoint has not been created, click New.
    1. Enter a name in the Endpoint Name field.
    2. Select Office 365 from the Endpoint Type drop-down menu.
    3. Select Provide Credentials or Do Not Provide Credentials as needed.
      1. If you select Provide Credentials, the form expands to present more fields for username and password. The credentials will be used by MigrationWiz to access the service selected. In most cases, you must provide credentials for an administrator account on those services, as this will enable MigrationWiz to have full access to the cloud service.
      2. If you select Do Not Provide Credentials, then MigrationWiz will request credentials from end users before a migration can be started. This may slow your migration, as you are now dependent on the end users to provide these credentials.
  9. Complete the Application (client) ID, the Directory (tenant) ID, and the Client Secret fields, otherwise, you cannot save your project.

    Destintation Settings.png

  10. Save, Go to Summary, then click Save Project.


When configuring the destination endpoint, do not forget to complete the client ID and the tenant ID fields for the Destination endpoint, otherwise, you cannot save your project migration.

Client Secret for Microsoft 365 Endpoints

For all Microsoft 365 Endpoints mailbox migrations (including archive migrations), MigrationWiz adds the Client Secret field, which is not always mandatory. 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 RBAC approach for application impersonation.

  • If you already have an admin account with the Impersonation role enabled (not using the RBAC approach) the client secret value is not mandatory. Please leave the Client Secret field empty.

Once the information has been provided for both, the source and/or destination endpoint, and the customer selects Save and Go to Summary, MigrationWiz performs an endpoint validation check for the Microsoft 365 endpoint.

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

Add Users

Add the accounts that will be migrated, which are also referred to as items, to a project using one of the following options:

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
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.
Add from MSPComplete
This option allows you to add users that you may have previously added to the customer in MSPComplete or a different workload.

Advanced Options

Support Tab

  • SuppressMeetingInvitationException=1 When migrating calendar invitations, the MIME content of the mail body confuses EWS and can slow the migration. This support option ensures that calendar invitations are migrated without throwing that exception.  All calendar invitations are created correctly on the destination even though EWS throws this exception.
  • MigrateHiddenInvitations=1 If your source consists of hidden invitations in a primary calendar that need to be migrated to the destination, please add the advanced option to enable those to migrate since they are not migrated by default. This advanced option is currently available only for G Suite (API) to Exchange Online (Microsoft 365) mailbox migration projects.


    Invitations migrated will not maintain a hidden status when using the support option.

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.


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


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

Migrating Gmail Labels

Two Advanced options are available to handle the migration of Gmail labels to the destination.

  1. Convert Labels to Folders: With this option, user labels from the source are converted to folders at the destination and mails are duplicated in each of their corresponding folders at the destination.

  2. Convert Labels to Exchange Categories: With this option, a single copy of all source mail will be migrated to a custom destination folder titled All Mail. All labels from the source are converted to Exchange categories and marked on each item at the destination. 

For steps and instructions, see Labels in G Suite Migrations.

Migrating Suggested Contacts (Other Contacts)

There are two recommended options, outlined in MigrationWiz - Email Migrations - FAQ.

  1. Migrate Suggested Contacts (Other Contacts): Contacts appearing under the ‘Other contacts’ label in Google Contacts will be migrated to the destination folder 'Suggested contacts'. These will not appear under primary My Contacts.

  2. Skip Suggested Contacts (Other Contacts): Contacts appearing under ‘Other contacts’ label are not migrated.

Run Migration

The following sections will guide you through running your migration. Each header is one step, with its component steps below. Follow these steps in order, and read the notes for important information about dependencies or best practices.

Run Verify Credentials

  1. Open the project containing the 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.

  5. Once complete, select the Status section and view the results of the verification.


  1. This is an optional step but allows you to retrieve the total folder and item count for the mail items in Gmail.

  2. Open the project containing items you wish to assess.

  3. Select the items you wish to assess.

  4. Click the Start button in your dashboard.

  5. Select Assessment from the drop-down list.

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

  7. Review the line items folder and mail count.

    1. Mailbox Size (bytes) will show the combined size assessment for selected item types (i.e. mails and/or contacts and/or calendars)

    2. Folder Count will show the combined count for emails, contacts, and calendars

      • Note that this is the total amount of folders, not the item count within the folders
  8. See The MigrationWiz Assessment Tool article for more details.

Notify Users

Send out the final notification that the migration is beginning. Include when the migration will start, the expected duration, any usage instructions during migration, and any expected steps or notifications for the post-migration timeline.

Pre-Stage Pass

  1. Select the users.

  2. Click the Start button from the top, and select Pre-Stage Migration.

  3. Under the Migration Scheduling section, from the drop-down list, select 90 days ago.

  4. Click Start Migration

MX Record Cutover

Once confirmed that the Pre-stage migration has been completed successfully. Log into the DNS provider's portal, and change the primary MX record to reflect the DNS settings for the destination O365 tenant.

Full (Delta) Pass

  1. Select the users.

  2. Click the Start button from the top.

  3. Select Full Migration.

  4. Select/ Unselect check boxes (for Contact, Calendars, Mails) based on your migration need.

  5. Click Start Migration.
    This migration should be completed quickly since most data is migrated during the Pre-Stage migration. 

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. Select the mailboxes that have migration errors.

  2. Click the Start button.

  3. Select Retry Errors from the menu.

  4. 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.

Post Migration

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

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