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Understanding Hard Bounces

Hard bounces usually indicate a permanent delivery problem such as a nonexistent mailbox or invalid domain and should not remain in active sending lists.

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Hard vs soft bounces

Hard bounces are permanent failures. Soft bounces are temporary (full mailbox, greylisting, brief outages). Treat them differently in suppression logic.

Repeated soft bounces can still harm reputation; define a threshold for moving chronically soft-bouncing addresses out of active sends.

Prevention beats cleanup

Verify at capture and re-verify aging lists so hard bounces never become a campaign surprise.

When a hard bounce does occur, suppress immediately and check for typos only if the user is still online in a product flow.

Action checklist

  • Suppress confirmed hard bounces
  • Check whether the address was mistyped
  • Verify older records before re-engagement
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