Need explanation of this error

Question

When I try to send a message using Transport.send(message) in this class:
import java.util.Properties;
import javax.mail.*;
import javax.mail.internet.*;
import javax.swing.*;
import java.awt.*;
public class Slanje {
     static String test;//THIS STRING WAS USED FOR TESTING
     Properties props = System.getProperties();
     Session session = Session.getDefaultInstance(props, null);
MimeMessage message = new MimeMessage(session);
     public void infos(String host,String from,String to,String subject,String messagetext) throws Exception {
     System.out.println(host+from+to+subject+messagetext);
//here I test all information and everything is OK
props.put("mail.smtp.host", host);
message.setFrom(new InternetAddress(from));
message.addRecipient(Message.RecipientType.TO,
new InternetAddress(to));
message.setSubject(subject);
message.setText(messagetext);
// Send message
public void posalji()throws Exception{
     System.out.println("I'm in");
     Transport.send(message);
     test="Success";//static String belongs class Slanje for test
But I get following message:
javax.mail.SendFailedException:Sending failed
nested exception is:
class javax.mail.MessagingException:
Could not connect to SMTP host:
local host,port 25;
nested exception is
java.net.ConnectException:Connection refused:connect
Please help me!

Answer 1

The message is self explanatory. The SMTP server that you tried to send the message through refused the connection.
This could mean several things:
1) You are using the wrong address/hostname
2) There is no SMTP service running on the machine you are pointing at.
3) You are behind a firewall and port 25 is turned off outbound.
4)???