If you submit to a server-side script such as PHP or ASP.net you may bypass client-side email software such as OUTLOOK, and respond with a success/failure message or redirect to a success/failure URL.
Your client's may need to enable a compatible default PDF viewer such as Adobe Reader in order to submit PDF forms, but, it's possible to respond with a success/failure with server-side scripts without the need for OUTLOOK.
For online examples: