Swaks is a featureful, flexible, scriptable, transaction-oriented SMTP test tool written and maintained by John Jetmore. It is free to use and licensed under the GNU GPLv2. Features include:
- SMTP extensions including TLS, authentication, pipelining, and XCLIENT
- Protocols including SMTP, ESMTP, and LMTP
- Transports including UNIX-domain sockets, internet-domain sockets (IPv4 and IPv6), and pipes to spawned processes
- Completely scriptable configuration, with option specification via environment variables, configuration files, and command line
The latest version of Swaks is 20170101.0, which can be downloaded as a package or a standalone script.
There is also a versions page which lists every released version of Swaks, complete with changelogs and download links.
The reference documentation from the latest release, which includes quick-start examples, is available. There is also an Occasionally Asked Questions document.