How to handle hard bounces, soft bounces, and complaints to protect your sender reputation and list hygiene.
⚡ Monitored by EmailExacto IntelligenceEmail bounces occur when a message cannot be delivered. Hard bounces indicate permanent failures (invalid address, blocked mailbox). Soft bounces indicate temporary issues (mailbox full, server unavailable). Complaint handling — processing spam button clicks via feedback loops — is equally important for reputation management.
Bounce information is returned in SMTP response codes. Hard bounces typically return 5xx: 550 5.1.1 Mailbox does not exist. Soft bounces return 4xx: 421 4.7.0 Try again later.
Most ESPs handle soft-bounce retries and hard-bounce suppression automatically. The critical requirement is that your sending system processes these signals — removing hard bounces and suppressing complaint addresses before the next send.
High bounce rates signal poor list hygiene to ISPs and directly damage sender reputation. Gmail and Yahoo treat sustained rates above 2% as a spam signal. Complaint rates above 0.1% trigger filtering; above 0.3%, bulk blocking begins. Unprocessed complaints — continuing to send to people who've marked you as spam — accelerate reputation damage dramatically.
EmailExacto monitors the downstream effects of poor bounce handling — blacklist listings and reputation changes that indicate a list hygiene problem.
✓Remove hard bounced addresses immediately — never retry a 550 hard bounce.
✓Implement a suppression list that persists across all campaigns and systems.
✓Set up feedback loop (FBL) integrations with major ISPs to receive complaint notifications.
✓Monitor bounce rates per campaign — a spike indicates a list quality or infrastructure problem.
✓Validate email addresses before adding them to your list.
✓Consider double opt-in to reduce invalid addresses at the source.
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