Have reviewed your install. It was not working because sh404sef was incorrectly rewriting the URL. I've removed those rewrites from sh404sef and created a Joomla menu item to the send email form. Appears to be working fine now in my tests. CB has rewrite rules for this URL, but sh404sef does not appear to care and rewrites it to whatever it likes for some reason. If you've any further issues please contact sh404sef and have them provide instructions for excluding the URL from their rewrite rules.