Linux is a version of the UNIX operating system that has gained popularity in recent years. As an operating system, it is reliable, stable, and can be downloaded for free. Due to these factors, Linux is used as the operating system of choice by various Internet Service Providers and other users.
The Linux kernel (kernel) was created by a Finnish student, Linus Torvalds, who called it Linux. Torvalds then made this code available to the world for free and invited others to add it as long as they kept their contributions free. Thousands of programmers around the world worked to improve Linux and it grew in functions and in number of users. Today, Linux has evolved to become a full-featured operating system and is poised to challenge the dominance of Microsoft Windows.
Due to the low cost and reliability of Linux, it has become a popular operating system for hosting web servers and email servers. Although Linux is more difficult to administer compared to Microsoft Windows, it offers more flexibility and configuration options.
There are several open source email servers available for the Linux platform. Open source is a term used for software applications whose source code is freely available. Programmers participating in the open source initiative freely share their source code for applications in the belief that by allowing anyone who is interested to modify the source code, the application will be more useful and bug-free in the long run. Open source applications are available at no charge. Linux is part of open source software.
Popular Linux-based open source email servers include Exim, qmail, and Qpoppter. Exim is a message transfer agent and was developed at the University of Cambridge. qmail is an Internet Mail Transfer Agent (MTA) and is a replacement for the Sendmail system included with Unix operating systems. qmail uses the Simple Mail Transfer Protocol (SMTP) to exchange messages with message transfer agents on other computers.
Qpoppter is one of the most used server applications for the POP3 protocol. It is compatible with the latest standards and includes a large number of optional functions. Unlike Exim and qmail, Qpoppter is not available for free.