I am having a problem sending with users sending a mail to one particular user/domain. I get the below NDR whenever i try to send a mail to this user/domain
The following recipient(s) could not be reached:
firstname.lastname@example.org on 6/29/2008 1:22 PM
You do not have permission to send to this recipient. For assistance, contact your system administrator.
<ourdomain.com #5.7.1 smtp;501 5.7.1 This system is not configured to relay mail (r) from <email@example.com> to firstname.lastname@example.org> for xxxxx.xx>
What might be the problem here ?