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The page link posted above should not be used. Knoppix has sendmail and smail.

whereis smail

smail: /usr/sbin/smail /etc/smail /usr/lib/smail /usr/share/man/man5/smail.5.gz...

Knoppix also has sendmail installed. I will learn to configure sendmail.
Info here: http://brennan.id.au/12-Sendmail_Server.html

At a glance, the issue is minor. There are solutions available on the internet. For example, this
(1) How To Install and Configure Postfix as a Send-Only SMTP Server on Ubuntu 14.04 at...