Drupal Mailing Solutions in Exchange Server 2010 Vicinity

Background:

I have faced an issue and through earlier that it was MimeMail bug, later realized it was at deeper level, ie. smtp security realms

Intro
Drupal is typically hosted on public linux web environments, whereby, this issue is irrelevant.

It is MS Exchange Server 2007 & 2010 envronment that needs a little attention to get things working.

Possible Issue
I recommend using the PHPmailer SMTP Library Module along with MimeMail
PHPMailer comes with advanced stmp setting which allows you to view Mail Server Reponse Log.

I recently was not able to send test email, though I was authenticated successfully, and noticed this line appears in the response log:

"550 5.7.1 Client does not have permissions to send as this sender"

Having googled around, I found this description

In response to "MAIL FROM:".
The "MAIL FROM" command specified an address at an authoritative domain, and the session does not have the ms-Exch-SMTP-Accept-Authoritative-Domain-Sender permission

This links describes the issue properly:

THIS IS VERY HELPFUL:
http://exchangepedia.com/2008/09/how-to-prevent-annoying-spam-from-your-...

But, yet, back to drupal, after reading the above page and being equipped with its understanding, I was still wondering for the following reason:

We have in our office other third-party CRM application that is happily authenticating with the mail server without facing the underlined issue above...

So, what is it that prevents drupal from interfacing happily with our mail server.

SOLUTION
Inside Drupal:

Site Configuration -> Site Information ::: Set EMAIL Address as ".....@....." (whatever)
Site Configuration -> phpmailer ::: Set smtp auth as "...." SAME ACCOUNT AS ABOVE

That is it.

With Best Regards
Bakr