Hey @Anv
I understand your frustration; and I’m sorry I don’t have more free time to debug all your SMTP relay problem every time you reply.
It seems like your SMTP mail host is receiving mail; but that does not necessarily mean it will work as an SMTP relay.
I recall, off the top of my head, there is a flag to use sendmail and other mail clients to check if the SMTP host is working properly as a relay. You might do some research on the sendmail -G option (or look for another way to test). Basically, you need to send the mail to a test email address different than the host you are working on, using your newly minted SMTP host as a relay.
Some History
In the old days, most SMTP hosts would relay mail out-of-the-box; but then all the SMTP hosts on the net became big SPAM boxes because spammers would just exploit the relay functionality (unknown to the owner of the box) and spam the world.
The bottom line is that you need to check to see if your newly minted SMTP host can relay the mail for you.
Did you look closely at your configuration tutorial and see if it mentioned setting up the SMTP host as a relay?
I’m just thinking out loud and hope this helps you in some small way get to the next step in your SMTP host project.