Lately we have been getting the following NDR when sending email to a particular domain:
firstname.lastname@example.org 16/10/2008 11:46 a.m.
The recipient could not be processed because it would violate the security policy in force
<domain.com #5.7.0 smtp;550 5.7.0 Access Denied>
The emails seem get through if we forward our mail through our ISP SMTP server.
What are we doing wrong?