To ensure that all unused teams expire and are deleted automatically, you need to configure a Microsoft 365 group expiration policy. This policy applies to teams because they are backed by groups. Here are the steps to follow:

Sign in to the Microsoft 365 admin center with your admin credentials.

Go to Groups > Expiration.

Turn on the Enable expiration toggle.

In the Group lifetime box, enter 365 days or select it from the drop-down list. This means that the teams will expire 365 days from their creation date.

In the Select group types to apply the policy section, check the Teams box. You can also select other group types if you want.

In the Choose how to handle owners of groups without owners section, enter adminLOD-Se551723.onmicrosoft.com as the email address to receive notifications for the expiration of orphaned teams. You can also add more email addresses if you want.

Click Save to apply the policy.

That’s it. You have successfully configured a group expiration policy for teams. This policy will automatically delete the teams that are not renewed by their owners before the expiration date. You can also view and restore the deleted teams within 30 days from the Deleted groups page in the admin center.