Contact form on testing server sends cc: to sender but not to us.

Been using the contactus.php page on our site for ages without fail. Now I'm testing it on a test server where my website will be migrated to and the form is not working properly.

CAPTCHA works, security question works, I get the Thank You page on submission and I get a cc: to the address I used to test the form. BUT the address where the form is directed to never receives the submission. Tested from several machines, OSes, even phones and tablets with the same result.

Confused as to how the submission works well enough to send the cc: back to the sender but not the original form to its intended target. (I've changed nothing from the presentsite – which still works fine – and the new testing server, and we've checked spam folders just to make sure the form email isn't getting derailed; it isn't.)

Note: Files are from the original Contact Form Solution Pack, just FYI.