http://www.shelldorado.com/articles/mailattachments.html

Sending e-mail using shell scripts

File attachments with MIME
  * mutt
  * MetaMail: mailto, metasend ftp://ftp.research.telcordia.com/pub/nsb/)

The most interesting command line arguments of metasend are listed in the
following table [refer to metasend(1) for a complete list].

-b	batch (non-interactive) mode
-c cc	CC address (for copy of the mail)
-f filename	Name of file to attach
-m MIME-type	MIME content type, e.g. "text/plain" or "application/octet-stream"
-s subject	Title (subject) of the mail message
-t to	Recipient's address
-n	Next file attachment (needed for multiple file attachments)
-D description	Description of the file content
-o outputfile	Name of an output file. If the -t option is given, the mail is sent directly to the addressee

  * mpack ftp://ftp.andrew.cmu.edu/pub/mpack/