Send email with codeigniter and ajax: aborted request

I'm using ajax to send an email through a contact form in codeigniter. The ajax (jquery) part is:

var dataString = 'nome=' +  nome + '&msg=' + msg + '&email=' + email + '&secure=' + secure + '&mailto=' + mailto + '&ci_token=' + $.cookie("ci_csrfprotection_cookie");

$.ajax({
        url: '<?php echo site_url();?>/contact/send',
        type: 'POST',
        data: dataString,
        timeout: 1000,
        dataType: "json",
        success: function(msg){
                if(msg.sent){
                    $('#feedback').html("<?php echo lang('email_sucesso'); ?>").delay(6000).hide('slow');
                        }
                        else{
                            $('#feedback').html("<?php echo lang('email_erro'); ?>").delay(6000).hide('slow');
                        }
                        botao.attr('disabled', false);
                    }
                });

And the controller is:

public function send()
{
    if ($this->input->post('secure') != 'siteform') {
        echo lang('erro_no_js');
    }else{
        $this->load->library('email');

        $nome = $this->input->post('nome');
        $email = $this->input->post('email');
        $msg = $this->input->post('msg');
        $mailto = $this->input->post('mailto');
        $secure = $this->input->post('secure');

        $config['protocol'] = "smtp";
        $config['smtp_host'] = "ssl://smtp.googlemail.com";
        $config['smtp_port'] = "465";
        $config['smtp_user'] = $this->settings['smtp_email'];
        $config['smtp_pass'] = $this->settings['smtp_password'];
        $config['charset'] = "utf-8";
        $config['mailtype'] = "html";
        $config['newline'] = "\r\n";

        $this->email->initialize($config); 

        $this->email->from($email, $nome);
        $this->email->to($mailto);
        $this->email->subject('Contacto do site');
        $this->email->message($msg);
        if ($this->email->send()){
            echo json_encode(array("sent"=>TRUE));
        }else{
            echo json_encode(array("sent"=>FALSE));
        }
    }
}

This actually sends the email correctly but the ajax call gets aborted and I never get a message back.

But if I remove the $this->email->send() bit, I get the response correctly but, of course, the email isn't sent.

What am I missing here?

Note: I have CSRF enabled and it's working ok in other ajax calls that query the database.

Try setting async to false like this.

$.ajax({
        url: '<?php echo site_url();?>/contact/send',
        type: 'POST',
        data: dataString,
        timeout: 1000,
        dataType: "json",
        async: false,
        success: function(msg){
                if(msg.sent){
                    $('#feedback').html("<?php echo lang('email_sucesso'); ?>").delay(6000).hide('slow');
                        }
                        else{
                            $('#feedback').html("<?php echo lang('email_erro'); ?>").delay(6000).hide('slow');
                        }
                        botao.attr('disabled', false);
               }
         });

Another way to try would be to use the complete function rather than the success function and lease async to true (which is the default). I think the complete function waits without a browser lock, but i'm not 100% certain of this.