How to send 'no' in form when checkbox isn

Question

In contact form 7 plugin of WordPress, Is it possible to send custom message to mail based on checkbox value. In my form I have, subscribe to newsletter checkbox. When user checks the checkbox, subscribe to newsletter is coming as 'Yes' in mail. Now I want to send subscribe to newsletter as 'No' when user doesn't check the checkbox.

Is it possible. I tried and am still searching for the answer in google but to no avail.Any help/suggestion is welcome. Thanks in advance.

Answer 1

Finally got the solution.

add_action("wpcf7_posted_data", "wpcf7_modify_this");
function wpcf7_modify_this($posted_data) {
    /* if checkbox isn't checked send Nej to mail */
    if ($posted_data['checkbox-829'][0] == "")
        $posted_data['checkbox-829'][0] = "Nej";

    return $posted_data;
}

I got this solution from answer of DACrosby here.