If you try to send e-mail from a system, whitch does not run an own e-mail-server (i. e. desktop system), you need to install something like nullmailer or esmtp, which forward your local mail to a "real" mail server.
As command line tools you can install mail or mailx (packages mailutils, heirloom-mailx or bsd-mailx). If you need attachments try biabam.