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. You can run it on Windows using Cygwin.)Exim is fast, flexible, and reliable. It is designed not to lose messages even if your server machine crashes. It can be used as a secure Internet-facing front-end to other, proprietary, mail systems used internally in your organization. Exim supports lookups from LDAP servers, SQL databases, and other data sources, letting you automate maintenance and configuration. It can work in conjunction with other tools for virus-checking and spam-blocking, to reject unwanted e-mails before they even enter your site. This book will help you deploy Exim as your SMTP e-mail server throughout your organization, and to configure, tune, and secure your Exim systems.