Glossary
Bounce rate refers to the percentage of emails that fail to deliver to recipients and are returned, or “bounced, by the receiving mail server. It’s calculated as:
Number of undelivered emails / Total number of emails sent * 100 = Bounce rate
For instance, if a brand sends 100 emails and 2 of those emails couldn’t be delivered, the bounce rate would be 2%.
2/100 * 100 = 2%
There are two types of bounces:
A high bounce rate can damage your sender reputation and impact inbox placement, especially with major inbox providers. That’s why bounce monitoring is essential for protecting deliverability. While an average bounce rate under 2% is generally considered acceptable, even a small spike – particularly in hard bounces – can trigger filtering or throttling.
Note: High bounce rates often point to stale lists, bad acquisition practices, or lack of list hygiene – not just technical issues.
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