Authentication problem

Hello,
      I am sending my mails through smtp.
      If my mail host is mail.multi.net.pk
      it works well
      If my mail host smtp.dia.sbcglobal.net
      I get error
      javax.mail.MessagingException: 530 5.7.0 Authentication required

my code is

      String host = "smtp.dia.sbcglobal.net";
      String filename = gDesc.getString("email_attachment");
      String msgText1 = "asdasdasd";
     String subject = "email_subject";
     Properties props = System.getProperties();
                props.put("mail.smtp.host", host);
     Session session = Session.getDefaultInstance(props, null);
     session.setDebug(debug);
        try {
         MimeMessage msg = new MimeMessage(session);
         msg.setFrom(new InternetAddress(from));
            InternetAddress[] address = InternetAddress.parse(to);
         msg.setRecipients(Message.RecipientType.TO, address);
         msg.setSubject(subject);

            MimeBodyPart mbp1 = new MimeBodyPart();
            mbp1.setText(msgText1);
            Multipart mp = new MimeMultipart();
            mp.addBodyPart(mbp1);
            msg.setContent(mp);
            msg.setSentDate(new Date());
          Transport.send(msg);
        }
        catch (MessagingException mex)
        {
         mex.printStackTrace();
         Exception ex = null;
         if ((ex = mex.getNextException()) != null)
            {     ex.printStackTrace();         }
       }
I want to work this code smae with host as smtp.dia.sbcglobal.net