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Deliverability

Quarantine

A holding area where suspicious emails are placed for review instead of being delivered to the inbox.

Definition

Quarantine in email refers to a state where messages are held for review rather than being delivered to the inbox or rejected outright. DMARC policies can specify quarantine for emails that fail authentication, meaning they may be sent to spam or held by the receiving server. Enterprise email systems often quarantine suspicious messages for administrator review.

Why It Matters

Understanding quarantine helps you interpret DMARC reports and deliverability data. If your emails are being quarantined, they are not reaching the inbox, impacting campaign effectiveness. Moving from a quarantine to reject DMARC policy represents increased confidence in your email authentication.

How It Works

When an email fails authentication and the sender has a DMARC policy of 'p=quarantine', the receiving server may move the email to spam, hold it for review, or flag it as suspicious. This is less severe than rejection but still prevents inbox delivery.

Best Practices

  • 1Start DMARC with 'none', move to 'quarantine' once you have verified all legitimate senders
  • 2Monitor DMARC reports when using quarantine to catch authentication issues
  • 3Plan to eventually move from quarantine to reject for maximum protection
  • 4Ensure all sending sources pass authentication before tightening policies

Frequently Asked Questions

Quarantine tells receivers to treat failed emails as suspicious (usually sending to spam). Reject tells them to block the email entirely. Quarantine is a middle ground while you verify your authentication is correct.

Check DMARC aggregate reports for messages that fail authentication. Monitor spam placement rates. Some ESPs provide deliverability dashboards that show inbox vs spam placement.