The admin quarantine feature provides greater email security and control by allowing admins to moderate when messages satisfying certain conditions are encountered in their domain’s mail traffic.
When a message is flagged by a policy for quarantine (e.g. subject contains the word ‘confidential’), it will not be delivered to the intended recipient. Instead, this message will show up in the admin’s quarantine review UI. Admins can then review the message, choose to allow delivery to the intended recipient, deny delivery with or without rejection notice or do nothing. If no action is taken, messages expire and are removed from quarantine after 30 days.
To make quarantine management easier, up to 25 named quarantines may be set up with unique quarantine criteria. Admins may choose to put messages in different quarantines based on several classification criteria by setting mail flow policies (content compliance, objectionable content, etc.).
Reference by : www.google.com