// Glossary
Bounce Rate
The percentage of sent emails that fail to deliver, a key signal mailbox providers use to judge a sender.
Definition
Bounce rate is the share of emails in a send that fail to reach the inbox, expressed as bounces divided by total sent. It combines hard bounces (permanent) and soft bounces (temporary). High bounce rates tell mailbox providers your list is stale or unverified, hurting sender reputation and deliverability. Keeping bounce rate low through pre-send verification and list hygiene is essential for inbox placement.
Why bounce rate is the metric to watch
Bounce rate is the share of sent emails that couldn't be delivered. Hard bounces (the address or domain doesn't exist) are the reputation-critical kind; soft bounces (a full mailbox or transient error) are temporary. Mailbox providers read a sustained high hard-bounce rate as a sign you don't maintain your list, and throttle accordingly. Public guidance puts the healthy line under roughly 2%, with 2–5%+ as risk. Because data age is the biggest bounce driver, verifying near send time is the most effective control.
Common questions
What causes a high bounce rate?+
Mostly stale data — addresses that were valid when scraped but have since been deactivated — plus typos, invalid domains, and unverified pattern guesses.
How do I lower my bounce rate?+
Verify the list close to send time, remove role-based and disposable addresses where appropriate, suppress prior hard bounces, and avoid sending to purchased lists that have decayed.
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