Erro ao enviar email

import java.util.Properties;
import javax.mail.*;
import javax.mail.internet.*;

public class SendMail {
    
    public static void main(String args[]){     
        
        String smtpHost = "smtp.com.br";
        String to       = "[email removido]" ;
        String from     = "[email removido]";
        
        Properties prop = System.getProperties();
        
        prop.put("mail.smtp.host", smtpHost);
        
        try{
            Authenticator auth = new Autenticador ();
            Session autent = Session.getDefaultInstance(prop, auth);
            
            Session session = Session.getDefaultInstance(prop, null);
                       
            MimeMessage message = new MimeMessage(session);
            
            message.setText("Teste OK");
            message.setSubject("Teste");
            message.setFrom(new InternetAddress(from));
             
            message.addRecipient(Message.RecipientType.TO,new InternetAddress(to));
                       
            Transport.send(message);
           
            System.out.println("Mensagem enviada");
        }catch(MessagingException e){
            System.err.println(e.getMessage());
        }
    }
}

Exception in thread "main" java.lang.SecurityException: Access to default session denied
        at javax.mail.Session.getDefaultInstance(Session.java:288)
        at SendMail.main(SendMail.java:21)
Java Result: 1