Mailx is an intelligent mail processing system, which has a command
syntax reminiscent of ed(1) with lines replaced by messages. It is
based on Berkeley Mail 8.1, is intended to provide the functionality
of the POSIX mailx command, and offers extensions for MIME, IMAP, POP3,
SMTP, and S/MIME. Mailx provides enhanced features for interactive use,
such as caching and disconnected operation for IMAP, message threading,
scoring, and filtering. It is also usable as a mail batch language, both
for sending and receiving mail.