Suppression list

Addresses you must never email again: unsubscribes, hard bounces and spam complaints, checked before every send.

The list lives across all tools and imports, so an address removed in one system is not added back by a CSV from another. It keeps you compliant with unsubscribe rules and protects the domain’s reputation, because mail to dead or unwilling recipients is what mailbox providers punish. Deleting a contact is not enough; the suppression entry must stay.

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Related terms

Hard bounce: A permanent delivery failure: the address or its domain does not exist or refuses mail.
One-click unsubscribe (RFC 8058): A standard way for mail apps to unsubscribe a reader with one POST request, required by Gmail and Yahoo for bulk senders since 2024.
Spam trap: An email address no real person uses, kept by a mailbox provider or a blocklist operator to catch senders with poor list practices.

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Przemysław Zalewski · 15+ years shipping software

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