What it is
Email quarantine is a mechanism used by mail security systems to isolate messages flagged as suspicious. Instead of delivering these emails directly to the user’s inbox, they are redirected to a controlled quarantine folder. Administrators or users can then review quarantined messages to determine whether they are legitimate or malicious.
Quarantine policies typically apply to messages that fail SPF, DKIM, or DMARC checks, or those containing malware attachments, phishing content, or policy violations. By holding these emails in isolation, organizations prevent potential compromise while avoiding false positives that could block legitimate communication.
Why it matters
Email remains the number-one attack vector. Quarantining provides a safety buffer, reducing the risk of accidental exposure to malicious links or attachments. It also offers valuable data for tuning spam filters and security policies.
How to reduce risk
- Regularly review quarantine reports and whitelist trusted senders.
- Educate users on verifying quarantined messages before release.
- Integrate quarantine alerts with security information and event management systems for correlation.
- Fine-tune spam filters using machine learning and user feedback.
- Apply retention limits and automatic purging to manage storage.