Bounce rate is the share of sent messages that a receiving server rejects. Hard bounces mean the address does not exist and should be removed at once. Soft bounces are temporary, such as a full mailbox or a busy server. The number is a diagnostic of list quality, not a performance metric to optimize away.
What it is
A bounce is a rejection notice returned by the receiving mail server, and the rate is bounces divided by messages sent. Hard bounces are permanent: no such mailbox, no such domain, recipient blocked. Soft bounces are temporary: the mailbox is full, the server is overloaded, the message is too large. The distinction determines the action. A hard bounce means delete the record. A soft bounce means retry later and delete only if it persists.
How it works
Most sending platforms suppress hard bounced addresses automatically, but the record usually survives in the CRM and gets re imported by the next campaign. That loop is how teams bounce the same dead address for a year. Bounces also carry a reason code from the receiving server, and reading those codes separates a list problem from a sending problem: rejections for unknown recipients point at the data, rejections for policy or reputation point at your domain.
Why it matters for winning clients
Mailbox providers use bounce behavior to judge senders. A high rate signals a list you did not build or did not maintain, and the penalty lands on every message the domain sends afterward, including invoices and client replies. It is also a client facing number: an agency reporting campaign results with a quiet bounce rate is reporting on a smaller audience than the client thinks it paid for.
Example in LeadCanvas
A studio prospecting local trades sees bounces climb on a list assembled from an old export. Rather than blaming the copy, it rebuilds the segment from current listings and checks contactability first. Our own July 2026 study of 231,349 deduplicated business listings found 15.8% of local businesses publish a phone and no website at all, and 33.6% in Brazil, so a share of any local list has no email channel to bounce in the first place and belongs in a calling workflow.
Common mistakes
Reporting one blended rate that hides which segment failed. Re importing hard bounced addresses because the suppression lives in the sending tool and the record lives in the CRM. Ignoring soft bounces until they harden. And treating a low bounce rate as proof of a good list, when catch all domains accept everything and produce an artificially clean number.
Related terms
Email verification is the check that prevents most hard bounces. Catch all domains are why the rate can look better than the list. Email deliverability is the outcome bounces damage, and data decay explains why yesterday's clean list bounces today. The links below open those entries.