Cannot send mail to SMTP contact

[meastaugh1]

Morning,

I have Exchange 2003, and have created an SMTP contact in AD. When I try to send to it, I receive a 5.1.1 NDR back. I've had a search around, but haven't come across anything obvious yet. The targetaddress is formatted as SMTP:a@b.com and mail is a@b.com. Can anyone suggestion which configuration change I need to make in Exchange?

Your message did not reach some or all of the intended recipients.

Subject: test
Sent: 22/01/2007 08:29

The following recipient(s) could not be reached:

ZZTestUserZZ on 22/01/2007 08:29
The e-mail account does not exist at the organization this message was sent to. Check the e-mail address, or contact the recipient directly to find out the correct address.
<SERVER.DOMAIN.COM #5.1.1>

[Geoff]

The user doesn't exist and/or doesn't have a mail box?