linux shell send and receive emails

http://www.netcan666.com/2016/02/20/%E5%88%A9%E7%94%A8telnet%E5%9C%A8%E5%91%BD%E4%BB%A4%E8%A1%8C%E5%8F%91%E9%80%81-%E6%8E%A5%E6%94%B6%E9%82%AE%E4%BB%B6/