You can now choose whether or not to allow your end users to view and deliver emails that have been quarantined. To configure this, go to Users>Default Policy>Allow end users to view and deliver quarantined messages. The default setting for this is 'Yes’.

When set to Yes, users can view and deliver quarantined messages from their message log or from the Quarantine Notification email.
When set to No, users cannot view, deliver, allow, or download quarantined messages.

Your end users might be trained to distinguish between legitimate and malicious email, but turning off this option will increase the overall safety of your organization.