Bounce
A failed email delivery. A hard bounce is permanent (address doesn't exist); a soft bounce is temporary (mailbox full).
A hard bounce signals an invalid address or a nonexistent domain: it must be removed from the list immediately. A soft bounce is temporary (server unavailable, quota reached) and can be retried.
Mailbox providers watch the hard-bounce rate closely: above a few percent it collapses sender reputation. Pre-send verification exists precisely to keep it low.
Related terms
To go further, read our B2B data enrichment guide or try the free email verifier.
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