463931 Fix e-mail routing issue

I have an e-mail routing issue that needs to be fixed urgently. I don't seem to be able to route messages sent from the contact form on my website to my own e-mail server (whereas if I change the destination e-mail address on the contact form admin to an external e-mail address - i.e. one that is not on my own domain - it works fine). Anyone out there who is familiar with this problem and knows how to fix it? Website is hosted with HostGator, e-mail server is hosted internally. Site runs on WordPress, tried both ContactForm7 and cFormsII with the same result.