Specifying how long spam messages are retained in quarantine
You can change the amount of time spam messages are kept before being deleted. You may want to shorten the retention period if quarantined messages use too much disk space. However, a shorter retention period increases the chance that users may have messages deleted before they have a chance to check them. The default retention period is 7 days. Only the administrators that have Full Administration rights or Manage Settings modify rights can modify quarantine settings.
By default, the Expunger runs at 1 A.M. every day to delete messages older than the retention period. For example, if you have a retention period of 7 days, when the Expunger runs it deletes all messages older than 7 days. The Expunger also deletes messages as necessary to enforce the Spam Quarantine message and size thresholds.