GNN Level Two will implement access control lists to block outbound traffic to port 25 (Simple Mail Transport Protocol—SMTP) from all systems except known, designated mail servers within your organization or network. Many bots, worms and viruses have their own SMTP engines and use those engines to send spam, viruses and phishing schemes from infected devices. By only allowing traffic to port 25 from specific IP addresses, you will be less likely to end up on a blacklist. This configuration is considered a best practice, and many commercial Internet service providers have implemented such services for their customers.
NOTE: Customers should be aware that this service is not a substitute for patching/updating machines or using anti-virus protection.