Quarantine disk
The quarantine disk stores the messages that are quarantined, including their attachments.
Depending on your spam actions configuration, the quarantine can contain also clean messages.
The messages are quarantined for the number of days defined in the quarantine settings.
What to do if the quarantine disk is filling-up
You can choose to store less data in your quarantine or to enlarge the quarantine disk.
Here are instructions for both of these options.
How to reduce the quarantine usage by storing less data
There are a few configurations that you can do in order to reduce the quarantine disk usage.
If you are currently storing clean messages in quarantine (i.e. you have the action "store" for the clean messages in your anti-spam settings) you can reduce the retention days for such messages (this can be done on version 4 and up) or decide not to store the clean messages at all. You can do this from the quarantine settings. Keeping clean messages in quarantine is useful for many reasons: being able to recover messages that the recipient accidentally lost and being able to report false negatives to esva labs are a couple of good reasons to store clean messages. Reducing the retention time for clean messages is therefore the first step that you might want to take before deciding not to store them at all.
If you are currently storing both spam and hi-spam messages in quarantine, you may want to decide not to store hi-spam messages. These are messages that have have been classified as spam with a high confidence so the chances that you will need to release them are slim. You can make this configuration from the anti-spam action settings.
Of course you can always reduce the quarantine retention days for all spam messages. This can be done from the quarantine settings. Based on your current quarantine disk usage and current retention time, you can estimate your average daily disk usage and adjust the retention time accordingly.
How to increase the quarantine disk size
The quarantine disk can be easily extended in size. It requires a brief shutdown, though.
The full procedure is documented here.