You are recieving 1000's of messages from a specific IP or range of IP's and need to block them.
This could be a spam attack or DOS attack.
Messaging Gateway can block an IP address (or CIDR range) from sending email into your environment by temporarily preventing an IP (or CIDR range) from connecting.
This IP or CIDR range should be removed from this list once the attack is over. This type of attack typically only occurs for a short period of time.