Finally, I caught the sendmail bug!

[Super-User]

To whom it may concern about configuring sendmail.

I had a good assistance from KCLUG.
I finally sorted it out since this morning configuring this sendmail.

Let me tell you what the solutions and problems were.

Solution:

There was a line on the sendmail.cf file in my case
/etc/mail/sendmail.cf

I had to add this line:
Cw infosavvy.tech.new.net

approximately, line number 82.

As a default, it was listed like this:
Cwlocalhost

I had to change this 
Cw my-domain-name

This document is found on page 100 in the book "DNS and BIND" published by
O'REILLY
which is my favoriate publisher.

The error message explained is almost(=exactly) same as that I had.

As a matter of fact, this line may not be necessary to some  sendmail that
is already configured as mailer.
I had a similar configuration before at my previous work place.

Well, my DNS configuration was okay.

Now, my system is singing as a name server, dns, and email server.

Thanks for your big help, anyway.

Joe Cho
A member of KCLUG.