Un peu dans le même style que swaks, voici sendemail

sudo apt-get install sendemail

Synopsis: sendEmail -f ADDRESS [options]

Required:
-f ADDRESS from (sender) email address
* At least one recipient required via -t, -cc, or -bcc
* Message body required via -m, STDIN, or -o message-file=FILE

Common:
-t ADDRESS [ADDR ...] to email address(es)
-u SUBJECT message subject
-m MESSAGE message body
-s SERVER[:PORT] smtp mail relay, default is localhost:25

Optional:
-a FILE [FILE ...] file attachment(s)
-cc ADDRESS [ADDR ...] cc email address(es)
-bcc ADDRESS [ADDR ...] bcc email address(es)

...

Pour modifier certaines valeurs (Message-ID, delimiter, X-Mailer...) le script /usr/bin/sendEmail est très simplement éditable.