You can use the soft bounce feature to manage emails that cannot be delivered to their next-hop IP address. Emails that cannot be delivered to their next-hop IP address are placed in the deferred queue while the Email Security - Server appliance attempts to deliver them. When soft bounce is enabled, emails that cannot be delivered before the queue timer has expired are moved to the bounced queue, where they remain until the bounced queue timer expires. You can enable or disable soft bounce and configure the number of days an email stays in any of the MTA queues from the Web UI and CLI.
If an email cannot be delivered and soft bounce has been disabled, the email is permanently dropped and a customizable non-delivery report is returned to the email sender. The non-delivery report can only be configured through the CLI.
Refer to the following topics for more information about enabling and disabling soft bounce and configuring the amount of time emails can remain in the bounced queue or any of the MTA queues.