Suppression list
The list of addresses you must never email again: unsubscribers, hard bounces, and recipients who marked your message as spam. It fills automatically.
Why it matters
It is the most effective protection for your sender reputation, and it requires no effort — except not circumventing it.
What enters on its own, and what does not leave. Three events add an address without being asked: an unsubscribe, a hard bounce, a spam complaint. A soft bounce does not enter — a full mailbox is not a closed door. And removing an address does not resubscribe anyone: the status stays 'Unsubscribed', a new signup from them is required.
It is the opposite of a mailing list: its job is to prevent. An address that enters it is excluded from all campaigns, even if an import adds it back to the database.
It fills itself — that is its main value, and why you do not have to think about it. Each workspace has its own, in addition to one maintained across the entire platform.
You do not clear it. Emailing someone who has unsubscribed is a violation, and one complaint costs far more than one subscriber.