Migrate Gmail to Office 365 - A step-by-step guide

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After the release of the cloud version of SharePoint, many organisations are looking to migrate all their data to SharePoint Online. Office 365 enable employees to seamlessly collaborate and engage with each other which will dramatically result in increasing their productivity. Migration to the cloud version of Office 365 has become a necessity since new features are being added to the SharePoint Online environment every day, and in order to keep up with these changes businesses should finally make the decision and migrate to Office 365.

Some people assume that migrating data to Office 365 is just coping data and pasting it the new environment, however Office 365 migration needs precise planning. Some of the steps of the migration are:

  • Source data trimming
  • Destination system designs
  • Source and destination data mapping
  • Content migration (ETL)
  • Testing and back up

You can either migrate data on your own or outsource the process, but remember data migration must be planned accurately, otherwise it might be time-consulting and in some cases lead into data loss. So, it is better to consult with an Office 365 migration expert before starting.

Here we have provided a step by step migrate Gmail to Office 365 guide. But before beginning on the tasks, let us define common methods of Office 365 migration:

  • Internet Message Access Protocol (IMAP) migration: You can use Exchange admin center or Exchange Online PowerShell to migrate user's mailbox content from an IMAP messaging system to Microsoft 365 or Office 365 mailbox. This migration involves migrating your mailboxes from other email hosting services, such as Gmail or Yahoo Mail to Office 365.
  • Cutover migration: With this approach all the users and mailboxes are migrated at once
  • Staged migration: This type of migration transfers data in two or more stages. Staged migration is not available for Exchange 2010 to Office 365.
  • Hybrid migration: A hybrid deployment gives you the unified look and feel of a single Exchange organization between an on-premises Exchange organization and Exchange Online on Microsoft 365.

Office 365 migration is full of headaches and need thoughtful preparations so make sure to choose the best Office 365 service provider company. As an instance, 365 Digital Consulting is a certified Microsoft partner specializing in Office 365 migration and SharePoint migration. Their Office 365 migration services encompasses all sorts of Office 365 migration scenarios like G Suite to Microsoft 365 (migrate Gmail to Office 365), SharePoint on-premise versions to SharePoint online, migrate between tenants, and many more.

How to get started for IMAP migration to migrate Gmail to Office 365?

We can migrate Gmail to Office 365 using the Internet Message Access Protocol (IMAP). Since Gmail supports IMAP, this type of migration is called IMAP migration.

IMAP migration has limitations. Including:

  • You can only transfer emails from the users' inbox. IMAP migration does not migrate contacts and calendar-related items from the source (i.e., Gmail) to Office 365.
  • In fact, contacts, calendars, users or administrators must be manually exported from Gmail and then imported into Office 365.
  • You can only transfer up to 500,000 items from one user mailbox to Office 365. The order in which emails are transferred is always from the newest to the oldest.
  • The largest email you can migrate using IMAP is 35 MB.

Remember to do the following tasks before starting your IMAP migration.

  • Before you can migrate to Office 365, you need to create Office 365 accounts for your users. Each user must have their own account in order to initiate the IMAP migration.
  • If you already use an email domain in your IMAP environment and planning to use the same email domain in Office 365, you must add that domain as an accepted domain to Office 365.

Migrate Gmail to Office 365 prerequisites

You can migrate the following functions from Google Workspace to Office 365:

  • Emails
  • Calendar
  • Contacts

You can also migrate Gmail to Office 365 in batches of users in various stages. For this type of migration, you need to define a list of users for each batch.

Here are two methods of Gmail to Office 365 migration prerequisites:

Automated - through the New Exchange admin center

Using the new Exchange admin center (EAC), migration of mails, calendars, and contacts from G suite to Microsoft Office 365 will be automated. This process has been simplified to the point where several steps that previously had to be done manually have been removed.

  1. In the new Exchange admin center, which is located at https://admin.exchange.microsoft.com/#/, open the Migration section and then choose Add migration batch.
  2. In this case, the migration batch wizard will be shown. On the first page, you should manipulate these settings:
  • Specify a unique name for the migration batch
  • Define the path of the mailbox migration: Check that the Migration to Exchange Online option is selected.

When you are done, choose Next.

  1. Select the Google Workspace (Gmail) migration option and then click Next, on the migration type page.


  1. On the Prerequisites for Google Workspace migration page, verify that the Automate the configuration of your Google Workspace for migration is expanded, and then click Start to automatically complete the four required steps.
  2. In order to validate your APIs, log in to your Google Account in the Google sign-in page that appears. The following things happen when your APIs are successfully validated:
  • A file in JSON format (projectid - *. Json) will be downloaded to your local system.
  • The link will be activated for you to add the ClientID and the Scope.
  • Click on the API access link. This will take you to the Google Admin API Controls page.
  • Click Add new, Copy the ClientID and Scope from the EAC, and then click Authorize.


  1. On the Set a migration endpoint page, choose one of these options:
  • Select the migration endpoint: From the drop-down list, choose the existing migration endpoint.
  • Create a new migration endpoint section: If you are a first-time user choose this option.



To migrate Gmail to Office 365 seamlessly, you need to have Office 365 connected to Gmail. To meet this approach, Microsoft 365 uses a migration endpoint. Migration endpoint is a technical term that defines the necessary settings which are required to migrate Gmail to Office.

If you have chosen the Create a new migration endpoint option, do the following:

On the General Information page, set the following settings:

  • Enter a value for the Migration Endpoint Name
  • For the Maximum concurrent migrations field, the default value is 20, leave it blank, or change the value if necessary.
  • For the Maximum concurrent incremental syncs field, the default value is 10, leave it blank, or change the value if necessary.

 Click Next when you have made these settings.

On the Gmail migration configuration page, define the following settings:

  • Email address:Enter your Google Workspace email address.
  • JSON key:Click on Import JSON. In the box that opens, find the downloaded JSON file option and click on it. Then choose Open.

After successfully implementing the endpoint, it will be added to the Select migration endpoint drop-down menu.

Pick the implemented endpoint from the list and then click Next.

  1. On the Add user mailboxes page, click Import CSV file and then select the path to the folder where the CSV file is located.

If you do not have this file, create a CSV file that lists all the users who needs to be migrated.

When you finish, click Next.

  1. Define the details on the Move configuration page, and then click Next.
  2. On the Schedule batch migration page, confirm all the details, click Save, and then click Done.

Manual - Using the New Exchange admin center as well as Classic Exchange admin center

Create a Google service account

  1. Sign in to your Google admin desktop using the Chrome browser. Its address is "admin.google.com".
  2. In a new tab, open the Service Accounts page.
  3. Create a new project and define the project name, then click Create.
  4. Choose and create service account, choose a name, select Create, and then click Done.
  5. Open the Action menu, select Edit, ss you will need this ID later, write it down.
  6. Go to the Show domain-wide delegation section.
  7. Choose Enable G Suite Domain-wide Delegation, select a product name, and select Save.
  8. once again Open the Actions menu and click on the Create key option.
  9. Select JSON and then Create. The private key is stored in the Downloads folder on your system.
  10. Select the Close option

Enable the APIs

You need to enable all the required APIs for your project.

  1. Open the Developer page for API Library and log in.
  2. Select the project you used in the Create a Google Service Account section.
  3. Look for these APIs; Each of them must be activated. Select the Enable option for them:
  • Gmail API
  • Google Calendar API
  • Contacts API
  • People API

Allow your Google tenant's access for the service account

  1. Go to the Google Workspace Admin page and sign in as tenant's admin.
  2. Open Security and then API Controls. Then click on Manage Domain Wide Delegation.
  3. Click Add new next to the API Clients list.
  4. Enter the clients ID.
  5. In the OAuth Scopes section, insert all the necessary scopes without spacing. Like the format below:

https://mail.google.com/,https://www.googleapis.com/auth/calendar,https://www.google.com/m8/feeds/, https: //www.googleapis.com/auth/contacts

Getting started on the Gmail to Office 365 migration

when you have fully done all the steps of the prerequisites such as verifying your own domain on Microsoft 365, adding users to the Office 365 environment, creating the list of Gmail mailboxes that you want to migrate, and connecting Google Workspace to Office 365, now it is time to start the main process. Here we have explained the steps in short.

Create a migration batch

In the classic Exchange admin center (classic EAC) you can utilize migration batches in order to migrate different groups of Gmail mailboxes to Office 365 all at the same time. This batches of Gmail mailboxes are the ones that you have listed in the migration file before. (Be aware that IMAP migration is not accessible through new EAC.)

To make sure the migration has worked properly go to Recipients > Migration in the Classic Exchange admin center, if the migration is successfully completed the status will show "Synced". If the status is "Failed" you should check the associated Mailbox status reports to spot the errors.

Verifying your successful migration to Office 365

After finishing all the steps, you should ask your users to follow the tasks below:

  • Sign in with the temporary username and password in the Microsoft 365 or Office 365 sign-in page.
  • Then they should change their password and update the time zone. If the time zone is not set correctly the calendar will be based on the wrong time zone.
  • Check Outlook to make sure all the emails and folders are there.



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