Email sent from the tenant management will be enabled only if the tenant has set the Performing tenant management setting.
When an operation such as registering a tenant or adding or changing a user has been performed, notification to that effect is sent to the tenant administrators, tenant users, and tenant email addresses within that same tenant.
Refer to "6.4 Settings for Sending E-mail" in the Setup Guide CE for information on how to change settings for e-mail sent from tenant administrators.