Form Validation When Empty

I have a page containing a basic form in asp. When the form is completed the information is passed to another asp file which generates an email and sends it to me. For example,

Joe Bloggs fills in the form requesting information. When he hits Submit the information is sent to me on email.

I have included form validation to catch any uncompleted form fields and prompt the user for information. But when i try and submit an empty form my validation is ignored and the form is submitted sending the email to me with no information.

I know the validation is correct because when i remove the Form Action property the validation works fine.