Configured exim4 on my server to send all mails externally

Hi, I'm running a Linode server, using exim4 for mailing service. I have a website - e.g. [login to view URL] - hosted on this server. On this website, I have a contact form - configured to send mails to info[at][login to view URL] (which is using Google Apps mail service). But every time people submit a contact form or purchase a product on my site, I can't receive the contact email or confirmation email. I did a bit research, they said because the email has the same domain with my website, the site lets the server send mails locally. But because my mail is setup using Google Apps, it is supposed to send externally. So now I need to re-configure the mail service to notify that mail is hosted in another server, not locally (it is called External mail exchanger as I remember).