>This is a bit contradictory. Your box is the default mail server for the domain,
>but they're using a different server for mail?
Exactly
>Can you simply delete the mail.virtualdomain.com entry? If it's not there, I think >it should look it up in the internet DNS records, which should have the MX >pointing at the real mailserver.
This changes nothing, unfortunately, I still get a polite message that the useraccount doesn't excist in my primary domain.
Just for testing purpose I made a useraccount with a matching accountname and tried forwarding mail from this account to the the remote mailserver. I got a message telling the mail is looping?? I seems as my box still think it should serve mail to the virtual domain.