Metric definitions · 6 min read
Email Bounce Rate vs Website Bounce Rate
Two different metrics share a name. Learn their distinct event sources, denominators, and missing-data rules.
Updated October 23, 2026 · Definitions and caveats are stated in the text.
Email bounce is a delivery outcome
An email bounce is a provider-reported delivery outcome, commonly classified as hard or soft according to the email service's event vocabulary. A reliable rate needs provider-supplied send data for the same scope and time window. A pixel cannot tell you whether a message bounced, and an empty provider integration cannot supply the missing denominator.
Define the numerator and denominator before publishing the rate. For example: verified hard-bounce events divided by provider-reported messages sent, with duplicate webhook retries deduplicated by event ID. If the provider does not supply a sent count, show the count that is observed and mark the rate unavailable or requiring integration.
Website bounce is a session rule
A website bounce is usually a description of a session with little or no engagement, but analytics products define engagement differently. In this tracker, the website bounce rule is configurable and documented: website bounce equals (eligible sessions minus engaged sessions) divided by eligible sessions. Engagement defaults to active time at or above the configured threshold, a minimum page-view count, or a conversion.
That is not a delivery metric and does not say that an email was rejected. A one-page session can still be valuable—for example, if the visitor completed the page's intended action—so interpret the rule in context.
Never blend the two denominators
Keep the cards separate, name their sources, and show the denominator. Email bounce uses verified provider data; website bounce uses eligible destination sessions under the configured engagement rule. Retries are deduplicated for provider events; automated or missing sessions are handled according to the documented website method.
If provider send data is missing, email bounce rate is not zero. If there are no eligible website sessions, website bounce rate is not zero. Both are unavailable until a valid denominator exists.
- Email bounce: provider events ÷ provider send denominator.
- Website bounce: non-engaged eligible sessions ÷ eligible website sessions.
- A missing denominator means no rate—not a fabricated percentage.
Questions
Can an email bounce rate be calculated from tracked opens?
No. Opens do not describe delivery outcomes. Email bounce events and the sent denominator must come from a verified provider integration.
Is a website bounce always a failed visit?
No. It depends on the documented engagement rule and the page's purpose. A single-page session may still complete the visitor's goal.