/ Glossary — Metrics
What is bounce rate?
The share of your sent mail that fails to deliver — a direct read on list quality and one of the signals providers watch most closely. Here's what's healthy and what isn't.
/ Definition
Bounce rate is the percentage of the emails you send that fail to deliver and are returned as undeliverable. It combines hard bounces (permanent failures, like invalid addresses) and soft bounces (temporary failures, like full mailboxes), and it's one of the clearest measures of how clean and current your list is.
It matters because mailbox providers read a high bounce rate as a sign of poor list hygiene, which damages your sender reputation and drags down delivery to your valid recipients. A healthy bounce rate is generally under about 2%, and a spike — especially right after importing a list — usually means the list wasn't properly validated.
/ In practice
What a healthy bounce rate looks like
As a rule of thumb, keeping your overall bounce rate under roughly 2% is healthy, with hard bounces ideally well below 1%. The number matters less than the trend and the cause: a stable low rate reflects a well-maintained list, while a sudden jump points at a specific problem — often a batch of unvalidated addresses from a recent import or a sending source that's newly broken. Because even one send to many invalid addresses can hurt reputation enough to affect valid recipients, watching bounce rate per send rather than only in aggregate is what catches problems early.
Lowering and maintaining it
Bounce rate is lowered the same way it's kept low: validate addresses at signup, use double opt-in, never import unverified purchased lists, and suppress every hard bounce immediately through a suppression list so a dead address is never mailed twice. Tracking soft bounces over time and retiring addresses that bounce persistently keeps the rate from creeping up. Watching it as part of deliverability monitoring turns bounce rate from a lagging report into an early warning.
/ Bounce rate and the bulk sender rules
A threshold providers now enforce
Bounce rate used to be purely a hygiene metric you watched for your own benefit. Under the bulk sender rules that Gmail and Yahoo now enforce, it's closer to a requirement: sending to high rates of invalid addresses is exactly the behavior those rules target, and a domain that does it risks filtering or rejection across all its mail. Keeping bounce rate low has shifted from best practice to a baseline condition of sending at scale, which is why automatic suppression and validation are no longer optional for serious senders.
/ Related terms
A low bounce rate is list discipline made visible. We keep it low.
Validation, automatic suppression, and monitoring keep your bounce rate down without you watching it. Bring us your sending and we'll keep the list clean.
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