A suppression list is a set of email addresses your platform will never send to — unsubscribes, hard bounces, spam complaints, and manually excluded contacts — used to protect deliverability and stay compliant.
In depth
Suppression is different from deletion: the record is kept precisely so those addresses can never be re-added or accidentally mailed again. Honoring the suppression list is also a legal requirement under laws like CAN-SPAM and GDPR.
Example
Hard bounces are added to the suppression list automatically after each send. Keeping them out helps hold bounce rate under the healthy 2% threshold and protects your sender reputation.
Related terms
Keep your list clean — see our email marketing guide.