What is Hard bounce vs soft bounce?
A hard bounce is a permanent delivery failure, such as an address that does not exist, while a soft bounce is a temporary failure, such as a full mailbox or a server that is briefly unavailable.
Hard bounces should be suppressed immediately. Mailing nonexistent addresses signals poor list quality to mailbox providers. Most email platforms do this automatically.
Soft bounces are retried for a period. If an address keeps soft bouncing across several sends, platforms generally treat it as undeliverable and stop mailing it.
Watching both tells you something about list health. Hard bounces cluster around bad data sources and typos, while soft bounces can point to temporary receiver issues or a mailbox that nobody uses.
A worked example.
A hypothetical jewelry store notices a small group of addresses bouncing after a trade show signup sheet was typed in by hand. The hard bounces are suppressed automatically, and the team adds address checks to the signup form so typos are caught before they reach the list.
Common mistakes.
- Re-importing suppressed addresses
- Treating every bounce as a temporary glitch
- Not validating addresses captured offline
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