Glossary

Soft bounce

Soft bounce

A soft bounce occurs when an email can’t be delivered due to a temporary issue, such as a full inbox, server downtime, message size limits, or sender reputation problems. These failures are usually outside the sender’s control and may be resolved on their own. 

At Mailgun, soft bounces are not automatically retried, but the recipient’s address is not suppressed. That means we won’t attempt to resend the same message, but future sends to the same address will still go through. 

Note: this differs from hard bounces, which are permanent failures and result in the address being added to a suppression list. 

Also worth noting: Soft bounces are distinct from deferrals, which indicate that delivery is still being attempted and hasn’t failed (yet). 

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