Definition
Bounce Rate
The percentage of sent emails that are returned to the sender because they could not be delivered to the recipient's address.
Why it matters in B2B outbound
Bounce rate is a direct proxy for list quality and a leading indicator of deliverability damage. When too many of your emails bounce, email service providers interpret this as a sign that you're sending to unverified or purchased lists — and they start filtering your messages to spam, even for the valid addresses on your list.
The acceptable threshold for cold email is below 2%. Above that, your sender reputation takes measurable damage. Above 5%, you risk domain blacklisting. Most experienced outbound operators aim for sub-1% bounce rates by running every list through an email verification service before any campaign launches.
There are two types of bounces: hard bounces (the address doesn't exist) and soft bounces (temporary delivery failure, like a full inbox). Hard bounces are the dangerous ones — they should be removed from your list immediately and never retried. Soft bounces can be retried after a delay.
How it works
To keep bounce rates low: verify every email address before sending using a tool like Prospeo, NeverBounce, or ZeroBounce. Remove any address marked 'invalid' or 'risky'. Use catch-all detection to flag domains that accept all incoming mail (which inflates deliverability scores but often results in silent bounces). Track bounce rates at the campaign level in your sequencer dashboard, and pause any campaign that exceeds 2% immediately to diagnose the list quality issue.
Related terms
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