Google to Office 365 Mail Migration Guide


  1. Google to Office 365 mail migration with Cloudiway
  2. Security
  3. Performance
  4. Mail migration scope
  5. Pre-migration configuration
    1. Before you start
    2. How it works
    3. Google IMAP Configuration
    4. Mapping Table
    5. Source Prerequisites
    6. Target Prerequisites
    7. Create your mailboxes
    8. Azure Active Directory Application
  6. Use the Cloudiway platform to migrate your Mailboxes
    1. Create Your Connectors
    2. Configure the global settings for migration
    3. Import or create your users
      1. Option 1: CSV import
      2. Option 2: Get List
      3. Option 3: Single user creation details
    4. Activate and monitor your migration
  7. Other migration options
    1. Resources Migration
      1. Rooms and Equipment
      2. Distribution List
    2. Migration of permissions
    3. Archive Migration
      1. Migrate existing archive mailboxes
      2. Migration to archives
  8. Troubleshooting



1. Google to Office 365 mail migration with Cloudiway

Cloudiway’s mail migration solution helps businesses perform elaborate technical migrations through a simple SaaS interface. As a result, mail migrations require no additional software installation or overhead, and migrations can be performed securely and quickly.

The Cloudiway new platform is flexible enough to support all types of migration paths. Your migration strategy will depend on your business setup, type, and size.

Whichever migration path you choose, Cloudiway provides all the essential features including license assignment, archive migration, and calendar coexistence (Free/Busy scheduling).

Two of the most common migration strategies are cutover and staged migrations.

Cutover VS Staged: The Best Migration Strategy


Cloudiway has developed a number of tools to enable seamless migration for the most intricate migrations. Our supplementary tools include:

  • Calendar Free/Busy display;
  • and, GALSync (Global Address Lists Synchronization).

Coexistence manages cross-platform communication with no impact on the end-user. It provides a seamless connection between two different remote systems during the migration. For example, a Google user can check the free/busy time of an MS 365 user. It also creates all users as contacts on both sides and keep the address books up to date.

To discuss any of these supplementary tools further, please get in touch with your existing Cloudiway contact.


2. Security

For more information about security, please refer to this article.


3. Performance

For more information about migration performance, please refer to this article.


4. Mail migration scope

4.1. What can be migrated and what are the limitations?

You will find what can be migrated and the limitations from Google Workspace (G Suite) to Office 365 on this page:

Google Workspace to Office 365: what is migrated and what are the limitations?

G Suite uses labels rather than folders to organize emails, and users can apply multiple labels to a single email. Office 365 mail doesn’t use labels, emails can be stored in only one folder.

When multiple labels are applied to one email, only one label is converted to a folder, for further information, please refer to this article.

4.2. Considerations

Migration takes place between existing mailboxes. This means that before starting a migration, mailboxes must exist in the target at the time of migration (steps are included in this guide).

4.3. Audience

This guide is aimed at experienced system administrators who are capable of connecting to remote systems and using a variety of administration tools.

Although we provide support for our own products, we do not provide support for third-party products such as PowerShell or server administration of Google or Exchange.

If you are concerned you might have any difficulty completing these steps, please consider a solution with our consulting team, contactable via this page. This will ensure a fast, cost-effective, and stress-free implementation.


5. Pre-migration configuration

5.1. Before you start

Before you start, you need the following accounts.

Name Description Location
Cloudiway Account to configure the Cloudiway Platform for your migration.
Google Admin To configure the Google feeds.
Office 365 Admin Used to configure Azure Active Directory Application and associated permissions.


5.2. How it works

The product uses IMAP and Google APIs calls to read the source.

Cloudiway uses Exchange Web Services (EWS) to migrate the mails, contacts, and calendars, and PowerShell for permissions, rooms, and resources.

Note: all network operations are performed over TLS 1.2.

5.3. Google IMAP Configuration

  1. Sign in to your Google Admin console using an administrator account.
  2. From the Admin console Home page, go to Apps > Google Workspace > Gmail > End User Access Google IMAP Configuration
  3. Select the organizational unit you want to configure settings for. If you want to configure settings for everyone, select the top-level unit. Or, select one of the child organizational units.
  4. Go to POP and IMAP access.
  5. Click the pencil “edit” icon.
  6. Check Enable IMAP access for all users. And Select Allow any mail client.
    You do not need to enable POP for Cloudiway tools to work.
  7. Save your settings.

5.4. Mapping Table

During the migration, Cloudiway uses a mapping table to perform the conversion of emails and permissions.

Important: the mapping table must be exhaustive, any missing email address will not be converted, and would end up with loss of permissions.

5.5. Source Prerequisites

To perform the migration, you need to configure the permissions (Google feeds).

This article explains how to configure a Google Workspace Connector and the Google feeds:

Google Workspace Connector Configuration

5.6. Target Prerequisites

We recommend creating an Office 365 account dedicated to the migration, that can be deleted once the migration is completed. This account is used only for PowerShell calls when migrating permissions, rooms, and resources. Other calls are done using the Azure Active Directory Application.

It must be configured with multi-factored authentication (MFA) and SSO (ADFS) turned off.

5.7. Create your mailboxes

The platform migrates between existing mailboxes. Therefore, the mailbox must already exist prior to the migration.

Resources from your source must be available in your target before migration can begin. Cloudiway provides a tool to automatically recreate rooms and equipment for migrations from G Suite to Office 365, which will be explained later in this guide.

5.8. Azure Active Directory Application

EWS calls are performed through an Azure Active Directory Application which is granted specific permissions.

You can either create an Azure Active Directory Application manually or let the platform create one for you.

Please consult our How To Create Azure Apps Registration page to create the Azure Active Directory Application and associated permissions.


6. Use the Cloudiway platform to migrate your Mailboxes

6.1. Create Your Connectors

For Cloudiway to migrate your Mailboxes, it needs to be able to communicate with both your source (GSuite) and target (Office365) domains. To do this, Cloudiway uses connectors. You will need to set up a connector for each source tenant you wish to migrate and each target tenant that mail should be migrated to. Follow the steps from the page below to configure your connectors:

Create Connectors Guide

For large projects, it’s possible to create multiple connectors that will be used in parallel. Please contact Cloudiway consulting services if you need to set up such configuration.

6.2. Configure the global settings for migration

Now that you have set up at least one source and target connector, you’re ready to configure your global settings. Using the Cloudiway platform, this is simply a matter of selecting what you want to migrate.

From the Mails area of, click on Global Settings

Mail Migration Global Settings

Most of the options are self-explanatory.

The Convert Email Address option needs further explanation. The Convert Email Address option is switched on by default (and is best left on). When activated, this option rewrites email addresses found in the header and replaces source email addresses with their corresponding target email addresses.

The mapping table is used for this conversion. Therefore, it’s important that all users exist in the mapping table before migration begins.

See the 7.3.2. Migration to archives section for further information concerning the calendar and the “Archive Mails Older Than” options.

Click on the Save button at the bottom of the screen to update your global settings.

6.3. Import or create your users

There are a number of ways to add users that you wish to migrate. These include:

  1. CSV file upload;
  2. Cloudiway’s Import Users tool; and,
  3. Create a single user.

Regardless, each user will need to be assigned a license type — Trial (limited to 100 MB), Education, Standard, Archive, or No License (used for adding users to your mapping table regardless of migration plans).

6.3.1. Option 1: CSV import

If you have a CSV file of all your users, you can upload the file to Cloudiway. The file must have the following fields in the header row:


How To Fill The Users/Groups CSV File?

  1. Ensure you’re still in the Mails Migration area of and go to User List Mail Migration User List
  2. Click on MANAGE and select ImportMail Migration Import User List
  3. If required, click on Download sample CSV and add your users to the CSV file using the sample headers (FirstName; LastName; SourceEmail; TargetEmail; BatchName)
  4. When you have a complete CSV file with the correct headers, click on the BROWSE button
  5. Locate your CSV file within your own file system, and double-click on it to select it
  6. Select the appropriate connectors in the Source and Target fields
  7. Click on the UPLOAD button. Upload User List for Mail Migration
  8. If you see any error messages, check your CSV file to ensure it has seven columns, each with a separator (including the last) and try uploading again.

6.3.2. Option 2: Get List

Cloudiway’s Get List tool helps you to retrieve users from your source tenant.

Go to Migration, select Get List.

Migration Get List

The tool requires you to enter the Source and Target Pool.

File Migration Get User List

Then to specify:

  • The Target Recipient Type: Standard, Shared Mailboxes, or Rooms and Equipment.
  • The Matching Rule:
    • Mail Exact Match: the source email = the target email ( >
    • Keep Email Prefix Same as Source: only the domain name changed ( >
    • FirstName.LastName (i.e.
    • F.LastName (i.e.
    • FLastName (i.e.
    • LastNameF (i.e.
  • The Target Domain.

It will then add new users to the User List. You can monitor the progress of this task in the User List: Get List Logs.

File Migration Get List Logs

6.3.3. Option 3: Single user creation details

Many of our first-time customers create a single user for testing purposes. This provides a means of watching the migration process without affecting all users.

Click on MANAGE > Create User and enter the following details:

Create User Mailbox Migration

For more information regarding the different fields, check out this article. Repeat the process for any more users you’d like to create.


6.4. Activate and monitor your migration

Now that you have performed all the pre-migration steps within your tenants and within Cloudiway, you’re ready to migrate. We recommend you run a test migration on a single user first to check that your configuration produces the outcome you expect.

To start your migration, select the users or batch you wish to migrate and click on MIGRATION then the Start button. Your batch will be scheduled and will begin as soon as resources are available.

Cloudiway Performance

Don’t forget that the Cloudiway migration platform supports delta passes and that migrations are therefore incremental; every time you restart the migration of a mailbox, only items that haven’t already been copied to the target will be migrated. The platform, therefore, does not duplicate items in the target.

Find out more about the delta pass:

Delta Pass During Mail Migration


7. Other migration options

7.1. Resources Migration

The Cloudiway platform provides a resource creation tool to customers performing mail migrations from G Suite to Office 365. Recreate rooms and equipment, Distribution List using the steps below.

From the same Mail Migration area, click on Global Actions Global Actions Migration

You can choose to migrate your Rooms, Distribution List. Migrating the Distribution List will recreate the list and the membership at the target.

7.1.1. Rooms and Equipment

In the Migrate Rooms section, click on START.

Select your Source that contains the rooms and equipment to be provisioned, click on START.Office 365 Rooms Migration

You will see a Scheduled status, and Completed when the process is finished.

Click on the User List sub-menu of the Mail Migration area and verify that all resources have been created in the User List.

7.1.2. Distribution List

In the Distribution List section, click on START.

Select your Source that contains the list to be provisioned, click on START.Office 365 Rooms Migration

You will see a Scheduled status, and Completed when the process is finished.


7.2. Migration of permissions

You can migrate permissions for mailboxes through the Cloudiway platform.

Migration of permission isn’t performed during the migration of the mailboxes but through a dedicated job.

The migration of the permissions will migrate permissions on the mailboxes, on the primary and secondary calendars.

Click on User List, select the users, go to MIGRATION, then click on Migrate Permissions

Migrate Permissions


NOTE: Once you start the process of permissions migration, it cannot be stopped.


7.3. Archive Migration

7.3.1. Migrate existing archive mailboxes

The Cloudiway platform migrates Google Vault archives, you can refer to the following admin guide:

Admin Guide: Mail Migration – from Google Vault mail archives

7.3.2. Migration to archives

The Google mailboxes can be migrated to the Office 365 mailboxes, to the Office 365 archives, or to a mix of both archives or online mailboxes.

Creating a partial archive of emails provides a number of benefits. From a migration perspective, the biggest benefit is reduced bandwidth. End-users who access mail via Outlook have their mailbox locally cached (in .ost file format). After a mail migration, Outlook will download all migrated mailboxes the first time users access their mailboxes.

For example, you could choose to migrate all items older than 30 days to a mail archive, which would be performed prior to the final cutover. The data will remain online and accessible from each user’s inbox as an In-Place Archive. The most recent 30 days of emails will be migrated and downloaded when each user first logs in, reducing overall bandwidth usage due to smaller mailbox sizes.

Note: you must ensure that In-Place archiving is switched on within your Exchange Admin center (you can bulk-activate using the instructions on TechNet as

From the Global Settings sub-menu, in the “Archive Mails Older” section:

Archive Mails Older

Enable Migrate to Archives, click on the calendar icon to select the date from where all older mails will be migrated.

Mails Older Calendar

Click on the Save button, when your migration starts, any emails older than the date you specified will be migrated to an In-Place archive. More recent items will be migrated to the target mailbox.


8. Troubleshooting

Cloudiway provides an extensive Help Center, also known as knowledge base, with many resources, including common error messages, guides, and downloads.

Please visit the Help Center here (where you can search for keywords or read through topics):

The Help Center also contains information on how you can ask for further support.

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