Soft bounce is a temporary email delivery failure, such as a full mailbox or a mail server that is briefly unavailable.
In depth
Unlike hard bounces, soft bounces may deliver on a later retry, so platforms typically re-attempt delivery for a period before giving up. Persistent soft bounces repeated over several sends should be treated like hard bounces and removed, as they may indicate an abandoned inbox. Common causes include an over-quota mailbox, a message that is too large, or a temporarily down mail server.
Example
An email to a recipient whose mailbox is full returns a soft bounce and may retry later.
Related terms
See our full email marketing glossary or the complete email marketing guide.