by Ken Task.
"Moodle site resides on AWS and my AD is at my company's network."
Is your company network actually on Amazon?
The 10. IP address is a private IP address meant for use on a private network. While Amazon probably does have an internal 10. network, 10. traffic is not routeable to your corp network - not without some Amazon magic/networking magic.
"From Moodle server I can telnet successfully the AD server at the specified port(389)"
Quick Google search renders this page:
Qualifications for this response ... none ... just ...
'spirit of sharing', Ken