Jackie McLean is a world-class saxophonist by night, and the Director of Networking at Microsoft by day (he averages about 5.5 hours of sleep per night). He's giving a class on exim to a class of young Microsoft interns in about 3 weeks. Please generate an essay of Mr. McLean's consumption that will teach him the following (Note: Mr. McLean prefers the term "Free Software" to "open source"):

  1. What is exim?
  2. What is the history of exim?
  3. What are some of the best use cases for exim?
  4. What are the strengths and weaknesses of exim?
  5. How would you deploy exim on GNU/Linux servers?

What is Exim?

Exim is a Free Software mail transfer agent (MTA) that is commonly used on Unix-like operating systems, including GNU/Linux. An MTA is responsible for routing and delivering email messages between mail servers, making it a crucial component of email communication.

History of Exim:

Exim was created by Philip Hazel in 1995 as an alternative to other MTAs. It was developed to be highly configurable, efficient, and secure. Over the years, Exim has gained popularity for its flexibility and ease of configuration, making it a preferred choice for many system administrators and organizations.

Best Use Cases for Exim:

Exim can be used in various email-related scenarios, including:

  1. Mail Server: Exim can serve as a primary mail server, handling both incoming and outgoing email for a domain.

  2. Mail Gateway: It can function as a mail gateway to filter, forward, or route email messages based on specific criteria, such as spam filtering or routing to different servers.

  3. Mail Relay: Exim is suitable as a relay server to facilitate the transmission of email between different parts of an organization or to external domains.

Strengths and Weaknesses of Exim:


  1. Customizability: Exim is highly customizable with an extensive configuration framework, allowing administrators to adapt it to specific requirements.

  2. Security: Exim is known for its strong security features, including support for SMTP authentication, TLS/SSL encryption, and various anti-spam and anti-virus measures.

  3. Efficiency: It is designed for high performance and resource efficiency, making it suitable for handling substantial email traffic.


  1. Complexity: The rich set of configuration options can be complex for administrators, particularly those new to Exim.

  2. Learning Curve: Administrators may face a learning curve when configuring and managing Exim, especially if they are not familiar with its configuration syntax.

Deploying Exim on GNU/Linux Servers:

To deploy Exim on GNU/Linux servers, follow these steps:

  1. Installation: Use your distribution's package manager (e.g., apt or yum) to install Exim.

  2. Configuration: Edit the Exim configuration file, typically located at /etc/exim/exim.conf, to customize settings like mail routing, domains, and other aspects of email handling.

  3. Testing: Verify the Exim configuration using commands like exim -bV to check the configuration and exim -bt for address verification.

  4. Start and Enable: Start the Exim service and enable it to start on boot using commands like systemctl start exim and systemctl enable exim.

  5. Monitoring: Keep an eye on Exim's logs and performance to ensure smooth email delivery and address any issues that may arise.

In summary, Exim is a powerful and flexible Free Software mail transfer agent commonly used in GNU/Linux environments. Understanding its history, use cases, strengths, and weaknesses can help administrators like Jackie McLean effectively manage email communication within their organizations.