Cannot forward to email at sub-domain

[cresedo]

Hi. A client has requested the following:

1. set up a subdomain and point it to a particular IP on a third-party server (i.e. mobile.domain.com --> 12.34.56.78)

This part worked fine. Then they asked:

2. forward all mail to user@domain.com to user@mobile.domain.com

This part does not work, as I get the error: "Warning: user@mobile.domain.com does not refer to a valid email account or alias. The address has been set to the main account). All email sent to user@domain.com will now be redirected to [main user]"

Any ideas on how to get this working would be most appreciated.

Kathryn

[cresedo]

Just to clarify, it's the subdomain's MX record that points to the external IP.

I also tried setting up the subdomain as its account instead, but doing it that way seems even worse, and the forwarding to an address on that domain (which is set up on the client's Exchange server) still doesn't route properly at all.