Per user Quarantine Area
Email Quarantine refers to the temporary restriction of emails that have not fully satisfied the security and policy requirements of the organisation.
Anti-spam proxy solutions provide the ability to provide each user the facility to be able to log into their own per user quarantine area that they are themselves able to manage. This means, rather than an administrator releasing false positives on a regular basis, on behalf of employees; individual users can manage their own email destined to their email accounts, and they can release their own emails if they feel it is a legitimate email. This is a massive burden off the administrator’s shoulders and a scalable option.
The user may also be able to whitelist the sender, which means future emails will reach their inbox. This feature is known as per user whitelisting.
Further Reading
Wikipedia's guide to Anti Spam Techniques