@url{https://www.gnu.org/philosophy/free-sw.html, free software}
licenced under @url{https://www.gnu.org/licenses/gpl-3.0.html, GNU GPLv3+}.
It should work on all @url{https://en.wikipedia.org/wiki/POSIX,
-POSIX}-compatible systems. Easy integration with existing
+POSIX}-compatible systems. Easy @ref{Integration, integration} with existing
@url{https://en.wikipedia.org/wiki/SMTP, SMTP} servers. Single
@url{http://yaml.org/, YAML} configuration file.