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. 

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.


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.

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.

What items are and are not 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 Meeting. Microsoft 365 doesn't 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.


  • 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.

Not Migrated in Any Instance

  • Calendar Reminders
  • Appointments
  • Chat message attachments
  • Google Groups for Business (including forums and collaborative inboxes)

Not Migrated As Source

  • Calendar Attachments
  • Calendar Reminders
  • Tasks
  • Chats and chat history
  • Email attachments that are links to Google Drive
  • Some calendar colors

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


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


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.
  • Only messages with the "Chat" label are migrated to the destination as an email message (without subject) by using the Advance Option MigrateChats=1
    • "Chat" label is a system label assigned by Google Mail and cannot be edited manually
    • "Chat" label is affixed to messages from the Classic Hangouts that went into the Inbox

Preparing the Source

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 and click on Apps > Additional Google Services and select the Google Cloud Platform. Once there, you should see a setting that can be toggled in order 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 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 select Create 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.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:


Preparing the Destination

  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.

Authentication Requirements

Exchange Online EWS Authentication Requirements

The two options 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. Select the option you wish to use for either your source or destination tenant. Use a Global Administrator for the configuration steps.

Important: Failure to perform the steps for one of the two required options for your Microsoft 365 endpoints, can result in failed jobs with 401 errors like the following in your project: Http POST request to 'autodiscover-s.outlook.com' failed - 401 Unauthorized

Regardless of the option selected, 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.

Of the two options available, the more recommended is the Modern Authentication option, as it is more secure. Configuring Modern Authentication to work with MigrationWiz and Exchange Online will be the default method by end of December 2022 due to Microsoft discontinuing support for Basic Authentication in Exchange Online. 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

Regardless of the option selected, 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

Basic Authentication Modern Authentication

BitTitan currently uses Basic Authentication by default for mailbox, archive mailbox, and public Folder migrations with Exchange or Exchange Online endpoints. The steps below do not apply to GCC or GCC High tenants. If electing to enable Basic Authentication for a GCC or GCC High tenant, a request will need to be manually submitted to Microsoft. The steps outlined below can also be found (with screenshots) here: Basic Authentication Deprecation in Exchange Online – September 2022 Update

Steps for enabling Basic Authentication in the tenant for Exchange Web Services


  1. Ensure you are signed into the O365 Admin Center as a Global Administrator.
  2. Click on the Help & Support icon (this is often a green icon on the lower right-hand corner of the O365 Admin Center page). This will open the Self-Help system. 

  3. In the search box under How can we help?, enter Diag: Enable Basic Auth in EXO

  4. Under Run diagnostics, click on Run Tests
  5. Once the diagnostic test completes, you will be given a dropdown list named Protocol to Opt Out

  6. From the dropdown list, select Exchange Web Services (EWS) and check the box for acknowledging the changes to be made.

  7. Click on Update Settings.

  8. After the settings have been implemented, it could take up to an hour before the settings take full effect in the tenant.

MigrationWiz Steps

Create a Mailbox Migration Project

  1. From 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 G Suite account which 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. Click Save, Go to Summary then click Save Project.

Add Accounts (Items)

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 o​ne at a time. Provide an email address for source and destination for each.

  • Bulk Add: This option allows you to add multiple items at once by copying and pasting from a spreadsheet or by importing a CSV file. The domain names at the Source and at the Destination might be different. Make sure to provide the right information in the project. If they are different, it's best to modify these in your CSV file, and then use the Bulk Add feature to import the users into the dashboard.

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

Purchase and Apply UMB Licenses

Licenses are required to run a migration project in MigrationWiz. To obtain license pricing information, or to purchase licenses, click the Purchase button in the top of your MSPComplete or MigrationWiz dashboard.

Payment: We accept credit cards, and wire transfer in certain situations.  

  • When purchasing with a credit card, payment is immediately processed during checkout. If successful, licenses are granted to your account instantly.

  • Wire transfers are available for purchases of 100 or more licenses. If you are purchasing at least 100 licenses, you will be presented an option to purchase via wire transfer during checkout. A wire transfer checkout will generate an invoice with wiring information for your accounts payable department and bank. Once the funds are received by our system, the licenses are granted to your account immediately. 

For this project type it is recommended to use our User Migration Bundle licenses. 

  • This license enables you to migrate the user's mailbox, documents and archive data.

  • Further information on User Migration Bundle Licenses:

    • User Migration Bundle Licenses have unlimited data available per license.

    • User Migration Bundle Licenses are applied to the customer's users, for whom you'll be performing migrations, and are valid for one year.

    • Read the MigrationWiz Licenses article for more information about how to apply the licenses to Users for migrations.

Set Project Advanced Options

Migrating Gmail Labels

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

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

  2. Convert Labels to Exchange Categories: With this option, a single copy of all source mail will by migrated 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 ‘Other contacts’ label in google contacts will be migrated to 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.

Migrate Chats

"Chat" label is a system label assigned by Google Mail and cannot be edited manually, it is affixed to messages from the Classic Hangouts that went into the Inbox. By default, Chats won’t be migrated with MigrationWiz.

In order to migrate these chat messages from Gmail to Office 365, you’ll need to add a support option into the advanced options. Currently, only English language messages are supported.

  1. Select Edit Project, then Advanced Options.

  2. Under Support/Support Options add: MigrateChats=1

Migrate Hidden Invitations

Hidden invitations from the primary calendar are not migrated by default. If your source consists of hidden invitations in a primary calendar that need to be migrated to destination, please add the advanced option to enable those to migrate:

  1. Select Edit Project, then Advanced Options.

  2. Under Support/Support Options add: MigrateHiddenInvitations=1

This advanced option is currently available only for G Suite (API) to Exchange Online (Microsoft 365) mailbox migration projects.


When migrating calendar invitations, the MIME content of the mail body causes confusion for 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.

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 mails, 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, 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 completed successfully. Log into the DNS provider's portal, 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/ Deselect check boxes (for Contact, Calendars, Mails) based on your migration need.

  5. Click Start Migration.
    This migration should complete 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 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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