MPK is a simple MIME packaging utility. Unlike
mpack and mmencode from metamail, it allows you to
encode multiple attachments in to a single mail
message. You specify attachment filenames on the
command line and optionally (with -m) provide a
text message on the standard input. A base64 encoded multipart message stream is produced to the standard output. It allows you to send SMTP email directly via a local MTA. Use -t for <to-addr> and -s for subject.