电子邮件编码特殊字符

我正在尝试使用SMTP协议和áéíó等特殊字符发送电子邮件库。问题是，即使使用UTF-8配置，电子邮件发送时也没有这个特殊字符。

我正在使用Amazon SES。

看代码

   //Libraries
   $ci->load->library('email');
  //Seta gMail
  $config['protocol'] = "smtp";
  $config['smtp_host'] = "ssl://";
  $config['smtp_user'] = "user";
  $config['smtp_pass'] = "pass";
  $config['smtp_port'] = "465";
  $config['smtp_timeout'] = 30;  
  $config['charset'] = "utf-8";
  $config['wordwrap'] = TRUE;
  $config['validate'] = TRUE;
  $config['mailtype'] = "html";
  $config['newline'] = "'r'n";
  $ci->email->initialize($config);
  //Carrega o modelo do e-mail
  $mensagem = $conteudo;
  //Seta variáveis
  $ci->email->from("cool@email.com", $titulo);
  $ci->email->reply_to('cool@email.com', 'New user');
  $ci->email->set_alt_message($conteudo);
  $ci->email->to($email_destino);
  $ci->email->subject($titulo);
  $ci->email->message($mensagem);
  $ci->email->send();