By adopting an appropriate migration vendor you can reduce the risk, time and cost of migration in order to achieve goal, with poor planning and migration strategy can stuck you in the middle of the ocean. Migration must be start by conducting a thorough pre-migration analysis of GSuite mailboxes, GDrive content and applications or devices which are using SMTP relay. Inventory all GSuite users, mailboxes and apps in order to capture the exact information needed to plan a successful migration.

Things to Consider for Migration;

  • GSuite user mail data size.
  • GSuite user mail data archive size.
  • Networking and Naming Services Planning.
  • Determine required tasks for configuring network and DNS.
  • Identify mailbox size and item counts that will be migrated to Office 365.
  • Determine mail-enabled applications and plan for configuration.
  • Conduct bandwidth assessment to calculate migration velocity for mailbox data.

Do you need 3rd party tool for migration?

Though GSuite migration connector is available in the Exchange Online but you should be aware of capabilities and limitations according to your requirements before buying any 3rd party tool.

The GSuite Connector has the following capabilities and limitations;

Few limitations to be aware of mailbox migration:

Rules will be migrated and remain turned off by default. We advise users to verify the rules on Outlook before enabling them.

  • Can only migrate EmailsMailbox Contacts and Rules (a maximum of 3 email addresses per contact are migrated), CalendarLabels.
  • Can’t migrate Vacation Settings, Automatic Replies, Filters, Room Bookings, Shared Calendars, Cloud Attachments, Google Hangout links, Gmail Tags, Contact URLs, Custom Tags.
  • Can migrate a maximum of 500,000 items from a user’s mailbox (emails are migrated from newest to oldest).
  • The biggest email message size you can migrate is 150MB.
  • Folder Manipulation.

Few limitations to be aware of Google Drive migration:

  • Can only migrate Google Docs, Sheets, and Slides (files are converted to the equivalent Office format including those over 10MB)
  • Can only migrate File and Folder Structure.
  • Can only migrate User Level Folder Permissions.
  • Can only migrate Group-Level Folder Permissions.
  • Can only migrate Files under 15 GB.
  • Can only migrate Basic Document and Folder Metadata:
  • Created Date
  • Modified Date
  • Created By
  • Last Modified By
  • Can’t migrate Ownership History, Previous Versions, and Comments.
  • Can’t migrate User-level file permissions
  • Can’t migrate Group-level file permissions
  • Can’t migrate Trashed items
  • Can’t migrate Google Drawings, Forms, Sites, and Maps.

Preparation of Mailbox Migration

Setting Up Routing Domains:

We need to configure sub-domains for mail routing purpose as shown in the following illustration;

GSuite to Office365 Mail Routing

Creating a Google Workspace Project

  1. Navigate to the Google Cloud Platform and sign in as a Google user (such as the Google Workspace admin).
  2. Click Create to create and name a new project for the onboarding (such as “Google Workspace project“), or click Select to select an existing project.

Create a Google Service Account

Creating Service Account

  1. Using a Chrome browser, sign into your Google Workspace admin console at admin.google.com.
  2. In a new tab or window, navigate to the Service Accounts page.
  3. Select Create project, name the project, and choose Create
  4. Select Create service account, enter a name, choose Create and then Done.
Grant access to the newly created Service Account

Open the Actions menu again and select Create key.

Choose JSON, then Create.

The private key is saved to the download folder on your device.

Enable API usage for the project

Navigate to the APIs page.
In the search bar, enter Gmail API.
Select it and then choose Enable.
Repeat this process for Google Calendar API, People API, and Contacts API.

If your project doesn’t already have all of the required APIs enabled, you must enable them.

Go to the Developer page for API Library and sign in as the Google user you used above in Create a Google Service Account.
Select the project that you used above.
Search for the following APIs, and then for each one, if necessary, click Enable to enable them for your project:

Gmail API
Google Calendar API
Contacts API

Enable Gmail API

Enable Calendar API

Enable Contacts API

Enable People API

Grant access to the service account for your Google tenant

  1. Go to the Google Workspace Admin page and sign in as Google Workspace admin for your tenant.
  2. Click Security, then click API Controls, and then click Manage Domain Wide Delegation.
  3. Next to the API Clients list, click Add new.
  4. In Client ID, type the ClientId for the service account you created in the Create a Google Service Account section above.

Configuring Migration Endpoint Connector

Navigate to Exchange Online Migration tab -> Migration Endpoints

Next to do;

Creating *.CSV files for user mailbox batches

Uploading batches and starting migration

Google Workspace GDrive to OneDrive for Business Content Migration

There are two options to migrate GDrive content to OneDrive for Business;

Microsoft 365 Migration App (Available in Google Workspace Marketplace)

Microsoft Mover


  1. Shared links won’t migrate
  2. Shortcuts won’t migrate
  3. Google Forms won’t migrate
  4. Support incremental sync
  5. Permissions on individual Files won’t migrate
  6. Permissions on Folders will be migrated only
  7. Version history won’t migrate

Reference: Mover Migration Tools overview and planning – Migrate to Microsoft 365 | Microsoft Docs

Migration info checklist;

  • Number of users to migrate
  • Data ownership
  • Data distribution
  • Amount of data to move
  • Number of files to move
  • Individual file sizes and/or file sizes on average
  • Who is your migration team?
  • Who is your designated contact with us?
  • Who is our point of contact with you?

Translating Permissions

If a folder (source) is shared with user “A” permissions for this user will be migrated to destination accordingly, but if user “B” don’t have permission on that Folder but have permission on some files , permissions for user “B” won’t migrate to destination.

How are permissions handled?

Permissions are handled in different ways depending on the source/destination connectors used.

  • When migrating data from a Single User Connector, permissions will not be applied to any migrated data.
  • When migrating from a non-Microsoft Administrative connector (such as G Suite or Dropbox), apply permissions at the folder level with the child folders inheriting those permissions.
  • When migrating from one Office 365 tenant to another Office 365 tenant using Office 365 (OneDrive/SharePoint Admin), apply permissions at the file level.

The above mentioned both applications have capabilities and limitations so if you are going to give up on some limitations and want to use free tool provided by Microsoft then “Microsoft Mover” is recommended.


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