Form not sending

We have two contact forms on our test site http://www.duzup.co.uk sending emails to louie@hexiweb.com. But both are coming back in a red box stating ” Failed to send your message. Please try later or contact the administrator by another method”. This site is hosted via 123 Reg on a plesk server but my email address is nothing to do with the site?

http://wordpress.org/extend/plugins/contact-form-7/