One of our users could not send an email to a specific email outside our domain. They got this error message bounced back:
Your message did not reach some or all of the intended recipients.
The following recipient(s) cannot be reached:
firstname.lastname@example.org on 18/08/2010 10:06 AM
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<mail.mydomain.com #5.5.0 smtp;571 Delivery not authorized, message refused>
I then raised the user's privileges to 'Domain Admin' and then he was able to send the email!
I'm assuming there is a permission issue on my mail server somewhere? Where should I be looking? Note: We are currently listed on a blacklist, we should get removed next Friday. Could this be a reason too?
Windows Server 2003