← Glossary
Delivery
What is Soft bounce?
A temporary delivery failure that the sending server retries.
How it works in practice
SMTP reports it with a 4xx code: a full mailbox, a server that's busy, greylisting or a reputation-based deferral. Retrying is normal. Repeated soft bounces at one provider are a signal to lower your sending rate.
The common mistake
Resending by hand on top of the queue's own retries.
Check it yourself
Related terms
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