Google Workspace Migration

How to Configure Exchange Online Licenses for Google Workspace Migration

Elise Williams Oct 20, 2026 868 views

Question details

The user needs to know how to correctly provision accounts and handle licensing for migrating Google Workspace mailboxes to Exchange Online.

How to Configure Exchange Online Licenses for Google Workspace Migration

Product: Exchange Online
Device & OS: not provided
Scenario: Migrating a batch of Google Workspace mailboxes to Microsoft 365, where accounts stalled during provisioning after assigning Business Basic licenses.
Observed behavior: After assigning Microsoft 365 Business Basic licenses, the accounts appeared as standard mailboxes instead of mail users, causing the trial migration to remain stuck during provisioning due to incorrect external email address configurations.

Before you start

Ensure you have global administrator or Exchange administrator privileges in Microsoft 365, access to the Google Workspace admin console, and an established routing domain.

Solution 1Recommended

Provision Microsoft 365 Accounts as Mail Users

Configure accounts as mail users and set up proper routing aliases before completing the migration.

To prevent migrations from stalling at the provisioning stage, accounts must be correctly formatted as mail users pointing back to Google Workspace until the migration is finalized.

Create accounts as Mail Users

In the Exchange Admin Center, ensure the migrated accounts are provisioned as 'Mail Users' rather than standard 'Mailboxes'. This allows them to route mail properly during the transition.

Configure the External Email Address

Set the 'ExternalEmailAddress' value for each mail user so that it points directly to their corresponding Google Workspace mailbox.

Set up routing domain aliases

Add the appropriate aliases to each account using your Microsoft 365 routing domain (e.g., alias@tenant.mail.onmicrosoft.com).

Verify settings and endpoints

Double-check the recipient type, routing addresses, and your Google Workspace migration endpoints in Microsoft 365 before resuming the migration batch.

Provision Microsoft 365 Accounts as Mail Users

Licensing Timing: Assigning licenses too early without setting the ExternalEmailAddress can convert the mail user into a standard mailbox prematurely. Apply licenses only after routing is configured.

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Frequently Asked Questions

Why did my migrating accounts become mailboxes instead of mail users?

This generally happens when a Microsoft 365 license (such as Business Basic) is assigned to the account before the ExternalEmailAddress attribute is correctly configured, triggering Exchange to auto-provision a standard mailbox.

What is a Microsoft 365 routing domain used for?

A routing domain (typically a .onmicrosoft.com domain) acts as a bridge that allows emails to be accurately routed between Exchange Online and Google Workspace while the migration is still in progress.

How can I change a mailbox back to a mail user?

You generally need to remove the Exchange Online license to deprovision the mailbox, then configure the ExternalEmailAddress attribute using Exchange Admin Center or PowerShell, and finally reapply the license.

Migration & Recovery