Suppression List
A suppression list prevents specified sends to an address. Preserve the reason and scope so opt-outs, invalid addresses, and complaints are handled correctly.
A suppression list records addresses that should be excluded from specified sends. The reason and scope matter: leaving one newsletter, opting out of all marketing, and reporting an invalid address are different states.
Apply the right restriction
A list unsubscribe should stop the messages covered by that request. A marketing opt-out should stop marketing. Neither is permission to bypass a delivery block when sending a receipt or password reset. Invalid-address and complaint suppressions may apply across sending paths, according to the provider's rules.
Keep suppression reasons and timestamps where your system supports them. Before sending, check both subscription permission and applicable delivery blocks. A contact's presence in an audience database does not establish either.
Preserve the decision during imports
Reconcile an import with current subscription and suppression state. An older export must not silently reactivate someone who unsubscribed afterward. Deleting a contact without preserving the necessary exclusion record can allow a later import to send to that address again.
Retain only the information needed under your privacy and retention policy. Remove a block only after establishing why it exists and whether the provider permits removal. A corrected address or documented resubscription needs a deliberate update. Clearing the whole list discards the reasons that stopped sending.