reCAPTCHA into FormM@iler

Can you give a tutorial on how to implement reCAPTCHA into your mail form?
I have a hard time making the 2 work.

I can make your mail-form work perfect.
Also using reCAPTCHA works.

But together they wont work, i can send mail while leaving the reCAP field blank or filled with jibberish.

And i didnt find solutions for it yet...