OpenSMTPD is a Unix system daemon implementing the Simple Mail Transfer Protocol to deliver messages on a local machine or to relay them to other SMTP servers. It has been released on the 17 March 2013 with version number 5.3 after being in development since late 2008.OpenSMTPD is primarily developed by Gilles Chehade, Eric Faurot and Charles Longeau as part of the OpenBSD project.