Block list – messages are blocked from being delivered when the sender's individual e-mail address, domain or IP address appear on this list. Learn more about setting up your Personal Block List.
Domain - suffix appearing after the @ symbol in an e-mail address. Characters after the dot identify what kind of organization you are dealing with (i.e. edu – educational; com – commercial, gov – government, etc.) Characters after the @ are domains within these categories (i.e. niu, aol, hotmail, etc.)
IP Address - every computer connected to the Internet is assigned a unique number known as an Internet Protocol (IP) address.