Codeigniter 3 email not sent in CLI mode

I have a task setup as a controller index function. If I call the controller directly from browser as localhost://app/cron the emails go out normally and arrive in my inbox. But when I call it from CLI as path/to/php path/to/index.php cron everything looks normal, no error is thrown in log files or on screen but emails are not delivered.

Even the following hack also outputs no error text.

if($this->CI->email->send()){
    echo 'Email sent to '.$email;
}else{
    echo 'Error sending email to '.$email;
}