A smart host is a type of mail relay server which allows an SMTP server to route e-mail to an intermediate mail server rather than directly to the recipient’s server. Often this smart host requires authentication from the sender to verify that the sender has privileges to have mail forwarded through the smart host. This is an important distinction from an open relay that will forward mail from the sender without authentication. Simple Mail Transfer Protocol (SMTP) is the de facto standard for e-mail transmission across the Internet. ... Wikipedia does not yet have an article with this exact name. ... An open proxy is an Internet proxy server which is accessible by unauthorized users, specifically those from elsewhere on the internet. ...

Use in SPAM control efforts

Some ISPs, in an effort to reduce SPAM originating at their customer’s IP addresses, will not allow their customers to communicate directly with the recipient’s mail server via Port 25. In this case the customer has no choice but to use the smart host provided by the ISP. An Internet service provider (abbr. ... View of a modern spam email, containing an advertising image. ... An IP address (Internet Protocol address) is a unique number that devices use in order to identify and communicate with each other on a computer network utilizing the Internet Protocol standard (IP). ... IANA is responsible for assigning TCP and UDP port numbers to specific uses. ...