Cold outreach operates with no prior consent and therefore no goodwill. Every technical and behavioral signal, including email bounce handling, is weighted more heavily by mailbox providers.
What email bounce handling is#
Bounce handling is the automated processing of delivery failure notices (DSNs) to classify hard versus soft bounces and suppress addresses accordingly.
Why it matters#
Repeatedly sending to invalid addresses is one of the strongest negative reputation signals providers track.
Applying email bounce handling to outbound#
- Parse DSN codes: 5.1.x means the address does not exist (hard); 4.x.x means temporary (soft).
- Suppress hard bounces after one failure and soft bounces after three.
- Route bounce notifications to a monitored mailbox or webhook.
- Review bounce reasons weekly for patterns like 'blocked' that indicate reputation issues.
Outbound-specific guardrails#
- Send from secondary domains, never the primary company domain.
- Cap each mailbox at 30 to 50 sends per day.
- Stop sequences on any reply, including informal opt-outs.
- Track reply rate as your primary quality metric.
Common mistakes#
- Treating 'mailbox full' as a hard bounce and losing valid contacts.
- Ignoring 'blocked by policy' bounces that signal a blocklist or DMARC failure.
Frequently asked questions#
What is the difference between a hard and soft bounce?
Hard bounces are permanent failures (bad address). Soft bounces are temporary (full mailbox, server down). Suppress hard immediately.