Quarantine can of course be deactivated. In this case, all messages, whether spam or not, are passed to the target server. You have the possibility to mark such messages with an individual marker in the subject. The header also displays the values "X-Recommended-Action: accept" or "X-Recommended-Action: reject", which can be used to filter the messages.
Please note: If quarantine is disabled, the sender will not receive an error message if his message is classified as spam. The error message is only displayed if quarantine is activated.