rouncube not send mail to Outlook

[nik]

Hi all
Need some help vestacp v0.9.8-21 . all is well except
hosting centos 6 vps wildcard dns + comodo ssl
Our mail server setup:
Domain ; our domain.com
AntiSpam Support - no
AntiVirus Support - no
DKIM Support - no

Problem
1) when user Post Ad using webmail ( e.g. yahoo , gmail etc ) no problem getting reply from RoundCube
2) however if use Post Ad with Outlook user get NO reply from RoundCube

Q. Am I missing any additional configuration
any help would be greatly appreciated