would be good to have and info displayed on admin. so admins can check their clients.
all leading email service providers offer that on the unsubscribe confirm page and its a good way to know why the subs unsub. could be:
A. Receiving to many emails
B. Never signed up to that email list
C. Not interested to receive emails anymore
and results will show up on /backend under the customers account so ESP`s admins and support staff can troubleshoot.
another safety net for ESP to check if anyone on their ESP doesnt follow permission based email marketing strategies