S-nail
An extended POSIX mailx(1) (moved to www.sdaoden.eu/code.html)
S-nail is a mail processing system with a command syntax reminiscent of ed(1) with lines replaced by messages. It is intended to provide the functionality of the POSIX mailx(1) command and offers (mostly optional) extensions for line editing, IDNA, MIME, S/MIME, SMTP and POP3. It is usable as a mail batch language.