Sendmail failed

[Mark Lo <markloky netvigator com>]

Hi,

     I am not able to send an email using my sendmail server !!

  I did try to use "sendmial -vt" to see what is wong with my machine.
after entering the command then i type the followings

To:markloky netvigator com
From:someone 3dsources com
Subject: Testing Sendmail

This is only a test.
.

After finished entering my messages...I put a period at the end then
press enter..then something pop up on my screen.

markloky netvigator com ....Connecting to  netvigator.com  via
esmtp......
>>EHLO space1.3dsources.com
250-..........pleased to meet you
250-expn
250-verb
and so on....

>>Mail From: <root space1 3dsources com> Size=100

then the error came out here......it states that

450 Unable to find space1.3dsources.com.

I would like to know what is happening here (450 Unable to find
space1.3dsources.com) , and also how come the mail is from
root space1 3dsources com  and not from someone 3dsources com   as i
stated in the From field.

I have set up my host name as space1.3dsources.com

Thank you

Mark Lo