Encountering error while creating a user for migrating from Google Workspace to Microsoft 365

Question

I followed the reference documentation to migrate from Google Workspace to Microsoft 365. I encountered problems when attempting to create "Mail Users" by assigning them an identity and specifying an "External Email Address" using a previously established redirection subdomain. However, since we are already using Microsoft Entra with licenses that include Exchange, the user already exists in Entra. Consequently, this user already has a mailbox listed in Exchange > Mailboxes. When I attempt to create a Mail User with the same name, I receive an error stating that the name is already in use, which is understandable. How can I create an "External Email Address" using the established redirection subdomain in this scenario? Reference: https://learn.microsoft.com/en-us/exchange/mailbox-migration/perform-g-suite-migration

Answer 1

Dear FineTech1,

Thank you for reaching out to Microsoft Community. I'm sorry to hear that you're encountering an error while creating a "Mail User" for migration from Google Workspace to Microsoft 365. This issue appears to be due to the user already existing in Microsoft Entra with an Exchange mailbox. I understand you are looking for an option to create an "External Email Address" using the established redirection subdomain for the existing user. While our primary focus is on Outlook-related issues, I would like to provide some guidance regarding your query:

To add an "External Email Address" to an existing user:

• Access the Exchange admin center
• Navigate to the Recipients section and select the mailbox you wish to update.
• In the mailbox properties, click on Mailbox and look for the option Manage email forwarding.
• Add the new forwarding address (to Google) here.

To add a "Routing domain" to an existing user:

• Access the Exchange admin center.
• Navigate to the Recipients section and select the mailbox you wish to update.
• In the mailbox properties, click on General and look for the option Manage email address types.
• Add the new routing email address from Google here.

After applying these settings, please verify if the issue is resolved.

If the issue persists or if additional assistance is required for Migration, I recommend posting your concerns in the relevant community. You can find specialized assistance in the "Microsoft FastTrack" section at Microsoft FastTrack - Microsoft Community Hub. Experts in this category have extensive knowledge of the migration issues and can provide tailored solutions to unique problems.

I apologize for redirecting you to a different community, but I believe this step will ensure faster and more accurate assistance for your specific scenario.

Thank you for your cooperation and understanding. Please do not hesitate to post your queries in the Microsoft Community, and we will always do our best to assist you.

Sincerely

Feroz Mahmud | Microsoft Community Moderator