The Barracuda Email Security Service is a comprehensive and affordable cloud-based email security service that protects both inbound and outbound email against the latest spam, viruses, worms, phishing, and Denial of Service (DoS) attacks. Spam and viruses are blocked in the cloud prior to delivery to your network, saving network bandwidth and providing additional DoS protection. You can see more information about this service like guide, how it works, ip ranges and many another information on their official site below.