How to enable Denial of Service attack protection in the Email Security?

What is a Denial of Service (DoS) Attack?

An assault on a network that floods it with so many additional requests that regular traffic is either slowed or completely interrupted.

To enable Denial of Service attack protection in the Email Security,

1. Please log in to the user interface as an admin user.
2. Navigate to Manage | Security Services | Connection Management and click the checkbox which says Enable DoS protection under Denial of Service (DoS) attack protection.

The Denial of Service attack protection can be triggered on receiving 10 to 7000 (can be configured by the user) connections from any given IP address in a single day. We can either defer future connections from the same IP address for different time intervals (1 hour to 1 year) or block future connections from the same IP address.

Specify the settings:

Trigger -- Specify the number of connections to allow from a given IP address.
Action to take -- Specify either to defer future connections from that IP address for a set amount of time or to block all future connections from that IP address permanently.

3. Please click Apply changes after you enable the Denial of Service Attack protection.

NOTE: Please don't turn on the DoS protection if you are not running email security as a first touch server. 

NOTE: If the navigation or the screenshot looks different from the one mentioned above , you may be in an older firmware version and would require a firmware upgrade. Please refer the link below to upgrade the firmware to latest version.

https://www.sonicwall.com/en-us/support/knowledge-base/170504270079039