To setup email auto-forwarding in Microsoft 365 admin center, please follow the below steps.

1. Login to the admin center and head over to the Users > Active users page

2. Select the user account for which the auto-forwarding rule has to be setup

3. Open the Mail tab and head over to Manage email forwarding.

3. Choose Forward all emails sent to this mailbox. Enter the forwarding address, and choose whether you want to keep a copy of forwarded emails.

Note: If you don't see this option, make sure a license is assigned to the user account.

Select Save changes after completing the setup.