Sup is an email client written in Ruby, originally by William Morgan, but now maintained and developed by the Sup community.
See below for platform specific instructions. Or you can refer to the general installation process.
Note that installing sup via both your native package manager and using instructions from this wiki will probably cause problems.
Note: We would like to encourage users of sup to contribute to and edit this wiki. If you discover erroneous information or if you use or configured sup in a way that may be valuable to others, please edit or add the information.