Unsubscribe request - customer with email [email protected] not found (PS8.1)

[DARKF3D3]

I have been using PS8.1 for a few weeks now and in the last few days I get errors like the following in the prestashop log:

Unsubscribe request - customer with email [email protected] not found

The email addresses are not of registered customers, only newsletter subscribers.
It is not clear to me where these unsubscribe requests come from and how in particular they return an error.

[musicmaster]

Maybe someone playing with the code and sending unsubscribe requests for non-existing email addresses. Try to find the ip address of the requests.