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

[rajibando]

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 https://www.digitalocean.com/communi...n-ubuntu-14-04
(2) Simple local smtp server - minimal setup ubuntu on https://superuser.com/questions/3472...l-setup-ubuntu
Requires postfix.
Postfix requires following dependencies, in chained order of pre-requisite:
postfix_2.9.6-2_i386.deb
mailutils_2.99.97-3_i386.deb
mailutils-common_2.99.97-3_all.deb
libmailutils4_2.99.97-3_i386.deb
libgsasl7_1.8.0-2_i386.deb

Finally, attempt to installation of postfix reports:
"clashes with smail"

I skimmed through the man page of smail.

... It is not intended to be a user interface for
reading and submitting mail. See mailx(1) on System V, Mail(1) on BSD
systems, or mail(1) on other systems for information on user inter‐
faces ...

I tried this command:

smail -bP '${smtp_hello_reject_hostnames}'

Elaborate output more than just the intended line in man page of smail:

localhost(\.)*;You've got to be kidding!  If you really were 'localhost' I'd be talking to myself!:.*\.localdomain;There is no such domain 'localdomain'!:.*\.test;There is no such domain 'test' -- it is reserved by IANA as per RFC 2606:.*\.example;There is no such domain 'example' -- it is reserved by IANA as per RFC 2606:.*\.invalid;There is no such domain 'invalid' -- it is reserved by IANA as per RFC 2606:.*\.localhost;There is no such domain 'localhost' -- it is reserved by IANA as per RFC 2606:(.*\.)*example\.com;There is no such domain 'example.com' -- it is reserved by IANA as per RFC 2606:(.*\.)*example\.net;There is no such domain 'example.net' -- it is reserved by IANA as per RFC 2606:(.*\.)*example\.org;There is no such domain 'example.org' -- it is reserved by IANA as per RFC 2606:${rxquote:hostnames}

Skimmed through man page of mail:

...
Sending mail
To send a message to one or more people, mail can be invoked with argu‐
ments which are the names of people to whom the mail will be sent. You
are then expected to type in your message, followed by a control-D (‘^D’)
at the beginning of a line. The section below, Replying to or
originating mail, describes some features of mail available to help you
compose your letter.
...

The /etc/mail.rc contains the lines:

set ask askcc append dot save crt
ignore Received Message-Id Resent-Message-Id Status Mail-From Return-Path Via Delivered-To

Easily understood.

A visual editor could also be used:

EDITOR Pathname of the text editor to use in the edit command and
~e escape. If not defined, /usr/bin/ex is used.

Now to exim4. Uses MTA. Details in https://packages.debian.org/wheezy/exim4
But also clashes with smail.
I am not amenable to remove something that is installed by Knoppix system developers.

I won't like to use the "mail" command, as it involves a lot of editing the system files and isn't very intuitive, one which is an automatic plus for visual email clients.

I have to set up a local smtp email server first through the tools available within Knoppix. Then, to use icedove or claws-mail. Without installing postfix as it clashes with smail.

I know 7.2.0 is an ancient version. But it works perfectly okay for me. So I don't wish to replace it. Doesn't require replacement at least, in the present case.

[rajibando]

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

[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?