S-nail provides a simple and friendly environment for sending and receiving
mail. It is intended to provide the functionality of the POSIX mailx(1)
command, but is MIME capable and optionally offers extensions for line editing,
S/MIME, SMTP and POP3, among others. S-nail divides incoming mail into its
constituent messages and allows the user to deal with them in any order. It
offers many commands and internal variables for manipulating messages and
sending mail. It provides the user simple editing capabilities to ease the
composition of outgoing messages, and increasingly powerful and reliable
non-interactive scripting capabilities.