Query: How to Set Up a local smtp email server from own system?

[rajibando]

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 /usr/share/man/man8/smail.8.gz

smail has its binary in "/usr/sbin/smail" and directory in "/etc/smail/" and within it has empty directories "methods" and "maps".

 whereis sendmail

sendmail: /usr/sbin/sendmail /usr/lib/sendmail /usr/share/man/man8/sendmail.8.gz

But sendmail binary in these two directories are only symbolic links.
Strangely Wheezy has the package sendmail and not smail. Searching with string smail in Debian Wheezy leads to "extsmail" and "asmail".
So my queries:
(1) What is the reason for choosing smail, instead of sendmail, exim4 or postfix, for instance, in Knoppix 7.2.0 based on Debian Wheezy?
(2) What is the origin of the package smail?
(3) When the package sendmail was tried for installation, it directed removal of smail. Why?
Found this guide:
Install Sendmail mail server on Debian GNU / Linux
[url=https://www.debian.org/doc/manuals/debian-reference/ch06.en.html#_the_mail_system]The current Debian Documentation[url] says that exim4 has most popular votes, postfix, second. Then sendmail.
But there must be a reason for Dr. Klaus Knopper's using sendmail and not exim4 or postfix. Would like to know the reason. In the man page for smail, it is mentioned:

... Smail was designed to be as close of a plug-in replacement for the BSD sendmail program as possible. External programs can call smail in very much the same manner that they previously called sendmail and expect similar results. ...

Which leads me to the question: Which External Programs?
Will uninstalling smail result in breaking of any other packages?