Glossary
What counts as a bounce, what a healthy number looks like, and how to fix a rising one.
In short
Bounce rate is the percentage of sent emails that were not delivered. Hard bounces are permanent (the address or domain does not exist); soft bounces are temporary (a full mailbox or a busy server). For cold email, keep bounces under about 2%; higher rates tell providers your list is poor and hurt the domain.
A hard bounce means the address will never accept mail: it does not exist, or the domain has no mail server. Remove it immediately. A soft bounce is temporary, such as a full inbox; retry later, and remove the address if it keeps failing.
Old or purchased lists, guessed addresses, typos, disposable inboxes, and domains without mail servers. A sudden spike can also mean your mailbox is being throttled by its provider.
Verify addresses before sending, remove role and disposable addresses, send to fresh lists, and keep daily volume steady. In Infiara, Safety Guard scans lists for invalid, disposable, and no-mail-server addresses and skips them at launch, and it slows a mailbox automatically when its bounce rate passes your limit.
Questions
Under about 2% is a common target. Above 5% is a warning sign to stop, clean the list, and check your domain setup.
Yes. Providers read high bounce rates as poor list quality, which can push future mail to spam.
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