Smail-3 is a software that functions as an Electronic Mail Transport Agent (MTA).
Smail-3 is a simple and user-friendly software designed to transmit mails. It is known for being one of the most straightforward and easy-to-configure mail transfer agents. Users can rely on its out-of-the-box configuration, which is ideal for small to medium-sized domains with little or no local customization needed.
The software is extremely capable and can meet the demanding needs of medium-sized businesses and ISPs. On a modest old P-II PC-class server with Smail and a decent mail store like Cyrus IMAP, it can comfortably handle all e-mail needs for tens of thousands of users. When run on enterprise-class hardware, Smail delivers enterprise-class service.
Smail-3 is relatively secure, utilizing secure and safe coding practices to guard against common pitfalls found in similar large programs written in C. While it has only ever been the subject of one security advisory, the software has strong defenses against network abuse, including denial-of-service attacks.
Moreover, as part of its defenses, Smail offers various access control features and filtering capabilities. Users can use several types of basic access control lists for implementing policies for SMTP clients, apply DNS-based access lists (IP and hostname-based) for different SMTP parameters, as well as full regular expression matching on content with separate passes for message headers and message bodies.
Smail-3 also checks for DNS consistency on client mailers and SMTP envelope sender addressees to provide anti-spoof protection for sender addresses in locally deliverable domains. It is essential to note that Smail-3 isn't intended for user interfaces for reading and submitting mail but instead functions as the interface to the network and mail delivery systems utilized by mail readers. The software is also not a mail store and does not provide services such as POP or IMAP. Nonetheless, Smail can work perfectly with other mail clients like Cyrus IMAP to provide those services.
Version 3.2.0.121: N/A