I have a problem with one of our customers. We installed an exchange server at his premises last year and so far sending / receiving email has been fine.
A few days ago our customer started getting the following error when sending or replying to email from our company.
email@example.com on 28/01/2008 09:38
There was a smtp communication problem with the recipents email server.
Please contact your system administrator.
<server.domain.int # 5.5.0 smtp;550 relay not permitted>
At this stage i am trying to discover if this is a problem with our customers exchange server or is it a problem with our excahnge server? We do not have any block lists setup and i am told my customer can email other companies without any real problem, however i am also informed this problem is experienced with a hand full of other email addresses.
Any help on this would be very helpful