email address and SMTP server

Good morning,

I'm having a problem with my SMTP server installed on W2k3 server.

Before we used SMTP of our ISP but because messages were delayed by few
hours on regular basis I decided to install SMTP server (Exchange server
installation is busted and will have to reinstall the server to get it
work). For now I have a problem with one address which is working from my
ISP's SMTP server but not from my server. I have setup my ISP's DNS servers
and there isn't problem with other recipients, only this one. I tried to
check the domain record for that email and it was OK. I checked via MX
record database what servers they are using and the servers were fine as

I got this response:

Final-Recipient: rfc822;

Action: failed

Status: 4.4.7

Is there any way how to check it or can you tell me what could be the

The domain is