Metrics
What is Bounce Rate?
The percentage of sent messages that fail to deliver and bounce back.
Bounce rate is the share of messages in a send that the receiving server rejects, calculated as bounces divided by total messages sent. It is usually split into hard bounces (permanent) and soft bounces (temporary), with the hard-bounce rate being the more reputation-critical figure. Mailbox providers watch this metric closely, and sustained high bounce rates lead to throttling, filtering, or outright blocking.
Why it matters for cold email
Cold senders should keep bounce rate low, commonly under about 2 to 3 percent, because providers read elevated bounces as a sign of a purchased or stale list, so monitoring it per inbox and pausing on spikes protects the whole sending operation.
Related terms
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