forward mail

[peman]

Hello,
One of our customer have only the website with us but the mail at their own SBS server. On their website they have a mailform that send mail to info@domain.com but everytime someone fills in the form i get a:
Undeliverable
Mail Delivery System <MAILER-DAEMON@portal2.hosting.com>
It says that it couldnt find the recipients email address. is that bacause it looks in the server itself?