E-mail is the most widely used application on the Internet. Exim is rapidly becoming one of the most widely used mail servers, handling mail for tens of millions of users daily. Exim is free software. It's easy to configure. It's scalable, running on single-user desktop systems as well as on ISP servers handling millions of users. (It's the default server on many Linux systems, and it's available for countless versions of UNIX.) Exim...