Create a Wordpress post with xmlrpc and jQuery
You cannot make a cross domain POST
request using jQuery or any other JavaScript technology. This is because of the same origin
policy required for security reasons. The only way you will be able to accomplish this is via a server proxy on the same domain, subdomain, protocol and port as the jQuery code.
Not sure what server technology you are using, but you could look into Simple PHP Proxy by Ben Alman.