Smail

Smail is a lightweight mail transfer agent (MTA) used on Unix-like systems during the 1980s and 1990s. It provides basic facilities for delivering, queuing, and transferring email between hosts and local delivery agents. Smail was designed to be compact and easy to configure, offering a simpler alternative to more feature-rich MTAs of the era.

Operation and design: Smail runs as a background daemon, maintains a queue of messages in a spool directory, and handles SMTP for network delivery as well as local submission. It supports standard features such as mail aliases, forwarding, and integration with local delivery programs. Configuration relies on plain-text files that define domains, addresses, and delivery rules.

History and usage: Smail saw use on smaller systems and academic networks where a minimal MTA was desirable. Over time, more capable MTAs such as Sendmail, Postfix, Exim, and Qmail became prevalent, and Smail was gradually phased out. Some historical Unix distributions included Smail as an alternative to Sendmail or as the default in earlier releases.

Legacy and relevance: Smail remains of historical interest for understanding the evolution of mail transfer software and for preserving older systems or archives. Its compact design and configuration approach are noted in discussions of MTA history and security practices from the period.