sendMail in javascript action

I have a javascript script being called by the HTTP binding. While calculating a return value works in the script, integrating a sendMail() value doesn’t. It throws an error in the HTTP binding like this: ab.binding.http.internal.HttpBinding] - Transformation 'JS(testEvent.js)' threw an exception. [response=...]
The sendMail() configuration seems to work, although I never sent a mail through openhab, but at least it doesn’t throw an error when mail.cfg is read.
The script I am trying to use is:

    (function(i) {
        var json = JSON.parse(i);
        sendMail("a@b.c", "Testsubject", "Testcontent");
        return ((json['state'])) == true ? "ON" : "OFF";

Do I have to include a library at the beginning of the javascript, or anything else to be able to access sendMail()?

I could solve this. I tried to implement a rule in a transformation script, and as it seems this is not possible. I set the rule in a .rules and then it all worked flawlessly.