Theoretically, every user has the possibility to log into the admin panel (https://login.europeanmx.eu) with his mail address, but this is not mandatory. A normal email user will only have access to his own mail address. As an admin you can access all blocked messages via the quarantine.
For example, to release blocked, valid messages from the quarantine, the admin can activate the option "Protection reports" (How can I be informed about blocked incoming messages?) or "Email Scout reports" (How can I create my own email scout reports and have them sent to me?) for the individual users. By activating this, each valid recipient will regularly receive an email from the system informing them about blocked, incoming messages and giving them the option to unblock and train them with one click, for example.
The actions which are available for a blocked message, can be regulated by the admin within the admin panel. You can restrict the report in a way that the recipient is only informed about blocked messages, but no options are available within the report. In order to release the message or to block the sender, he/she may then have to contact the admin.
You can manage the actions via "Reporting" > "Domain report actions".