Were having a problem with email bounceing back when sent to several organisations stating our IP is dul, the exact message is...
'email@example.com' on 10/11/04 12:24
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<server.domain.co.uk #5.5.0 smtp;553-mail rejected because your IP is in DUL. See>
Now I'm no expert, so correct me if I'm wrong, from looking around it seems this error is usually down to the IP address being on a black list which companies subsribe to to cut down on spam. One problem is usually the response comes back with a company to contact, or even the IP address that is being blocked which the above doesn't.
The server.domain.co.uk resolves to the IP address of our email/web hosting company and I would doubt that would be blocked, I've been in contact with them and they haven't been incredibly helpfull.
I've a sneaking suspicion this may be a problem with the setup in our exchange 2000, but not to sure where to start.
Any help much appreciated.