This measure is imposed to comply with the GDPR
In case your respondents wish to stop receiving emails from you, they can click on a link in the email they received.
You will find below a statement sent by Eval&Go. This statement is written at the end of each email.
"To stop receiving emails from this sender, please click here"
Clicking on it will automatically "unsubscribe" your contact from your list. His address will be added to the blacklist (in "contact manager").
Afterwards you will be blocked from sending questionnaires to that contact. Even if the contact is re-created.
This blacklist can not be deleted.