How long should addresses stay on a suppression list?
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You've probably hit send to a bad address and watched it bounce. Now you're wondering: do I delete it and try again later, or is it gone for good? The answer depends on what kind of bounce you got.
Hard bounces stay suppressed forever. If the email address doesn't exist, the domain doesn't accept mail, or the recipient explicitly rejected you, that's permanent. Remove the address from your list immediately and never send to it again. Mailbox providers track bounces. Sending to hard bounces tanks your sender reputation.
Soft bounces are temporary. These happen when the server is temporarily down, the inbox is full, or the message is too large. Your Email Service Provider usually retries soft bounces automatically (typically three to five times across different campaigns). Once those attempts fail, suppress the address for a few weeks or months, then consider a re-engagement campaign.
Unsubscribes and complaints are permanent too. If someone clicked unsubscribe or hit "this is spam," honor it. Those addresses stay suppressed forever, legally and reputationally.
The core principle: permanent failures (hard bounce, unsubscribe, complaint) never come back off your suppression list. Temporary failures (soft bounce) get a retry window, then suppression. You can track suppression status using your ESP's tools or a validation service. Don't guess about bounce classification. If you're unsure whether your list is properly classified, that's what our Blocklist Checker and SOS team can help with.
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