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Bounced email

(also bounce message)

Bounced email definition

Bounced emails are emails that failed to reach the recipient's inbox and return to you with a notification of their failure. This process involves several steps and can happen for various reasons, categorized mainly into two types: hard bounces and soft bounces.

See also: email retention policy, self-destructing email

Hard bounces

Hard bounces happen when the email address is invalid, non-existent, or the domain name doesn't exist. As soon as the sending server attempts to deliver the email and discovers the issue, it immediately classifies the email as undeliverable and sends it back to the sender with a failure message. This is a permanent failure, indicating the email will never get delivered unless the underlying issue, like a typo in the email address, is fixed.

Soft bounces

Soft bounces are temporary issues that prevent an email from being delivered. These can include a full recipient's inbox, a server that is temporarily down or too busy to accept messages or an email message that is too large. The sending server, after encountering issues like these, will try to deliver the email multiple times over a predefined period (often 72 hours) before giving up and returning the email as undeliverable. Unlike hard bounces, soft bounces suggest that the email might still be delivered if the temporary problem resolves.