How should I manage different types of suppressions?
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If your suppression list is one undifferentiated block of addresses, you're probably making at least one of these mistakes: retrying addresses you should have permanently blocked, re-adding people who asked to be left alone, or missing the feedback loop signals that would protect your sender reputation. Different suppression types carry different rules, and your system needs to treat them that way.
Hard bounces are permanent delivery failures: the address doesn't exist, the domain is gone, or the mailbox has been disabled. Suppress these immediately and permanently. There's no scenario where retrying a hard bounce improves your situation. It burns your sender reputation and signals to receiving servers that you're sending to dead addresses. Most ESPs suppress hard bounces automatically on first occurrence, but if you're importing lists from outside your ESP, validate them against your hard bounce suppression before you send.
Manual unsubscribes should be honored immediately, even though CAN-SPAM gives you up to 10 business days. Store the unsubscribe date and don't re-add without documented fresh consent. Under GDPR, you retain the address for suppression purposes only. Spam complaints from Gmail, Yahoo Mail, and other providers with feedback loops are the highest-priority suppression category: suppress immediately, flag them separately, and treat any future re-subscribe from that address with extra scrutiny before sending.
Soft bounces need a different cadence. These are temporary failures: a full mailbox, a server timeout, a greylisting delay. Your ESP will retry automatically for most of these, which is correct. But after three to five consecutive soft bounces over several weeks, the address is behaving like a dead one even if it's technically valid. Move it to suppressed at that point rather than continuing to retry indefinitely.
The goal across all types is a master suppression list that syncs across every platform you send from. If you use separate ESPs for transactional and promotional mail, a spam complaint received on one should suppress the address on both. Checking that sync is working correctly is worth doing on a quarterly basis. Once you've got your suppression types separated and synced, the related article on lawful grounds for retaining suppressed addresses explains what data you're actually allowed to keep for each category.
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