Hard bounces suppress the address permanently and immediately. Soft bounces retry with backoff, then convert to hard after repeated failures. Keep hard-bounce rate under 2% — above that, fix list quality before sending more.
Automatic handling
Hard bounce (address doesn't exist): immediate permanent suppression, exit from sequences, Golden Record flagged. Soft bounce (mailbox full, temporary rejection): retry with backoff up to 3 times, then treat as hard.
The 2% rule
A hard-bounce rate above 2% signals list-quality problems to providers and drags reputation. The dashboard alerts at 1.5%. Above 2%, pause and audit where the bad addresses came from.
Prevention
Pre-send verification catches most bad addresses before they bounce — enabled by default on all sequence sends. Bulk imports get verified on import; don't skip it to save credits.
Bounce forensics
Deliverability → Bounces shows bounce reason codes per mailbox and per audience source. A spike traced to one data source means demote or verify that source, not a platform-wide problem.
