What types of addresses should be on a suppression list (bounces, unsubscribes, complaints)?
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Your suppression list should contain any address that's signaled "don't mail me." That includes refusals, bounces, and high-risk addresses. Let's break down what goes in.
Hard bounces are the obvious one. If an email address doesn't exist or the mail server permanently rejected it, don't try again. Add it to suppressions immediately. A soft bounce (temporary delivery failure) should not go into permanent suppressions. Those usually recover, and the address might be valid.
Unsubscribes go in every time. Someone clicked "unsubscribe," they asked out, you respect that. Legal requirement under CAN-SPAM and GDPR.
Complaints (sometimes called Feedback Loop reports) matter because they're the mailbox provider telling you directly: this person hit the "spam" button. ISPs take complaints seriously. One complaint can hurt your entire reputation. Suppress those addresses immediately.
Role accounts that rejected your mail should also be suppressed. Abuse@ addresses, noreply@ addresses, and shared mailboxes that bounce or complain are often automated systems, not real recipients. Don't waste sends on them.
Spamtrap hits (if you ever discover one) go straight into suppressions. A spamtrap is a honeypot email address. If you're hitting them, it signals to ISPs that you're not maintaining list hygiene. Stop immediately and clean your list.
Why all this matters: Every address on your suppression list is one fewer bounce, one fewer complaint, one fewer deliverability penalty. A clean suppression list protects your sender reputation.
Next step: Learn the difference between hard and soft bounces so you know when to suppress permanently, and understand unsubscribe compliance.
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