My Webserver is located behind a proxy server. Every outgoing traffic is going through this proxy.
How can i tell the K2 google captcha plugin the proxy settings to enable traffic between my site (captcha) and google servers.

Hi. K2 just implements this. Have you set up correctly the keys and the domain under K2 parameters? If so, you need to refer to the reCAPTCHA page to see if what you want to do is supported. You can find more information at www.google.com/recaptcha.