Error al intentar enviar un mail

hola a todos, tengo una pequeña clase que intenta enviar un mail a traves de internet, pero no puedo aqui esta el codigo y enseguida el error que me devuelve

package mmp.usa.ejb;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;

import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.activation.FileDataSource;

import javax.mail.BodyPart;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Multipart;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.AddressException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;

public class Mail {
public Mail() {
}

public static void sendMail(String mailServer, String from, String to,
String subject, String messageBody,
String[] attachments) throws
MessagingException, AddressException
{
// Setup mail server
Properties props = System.getProperties();
props.put("mail.smtp.host", mailServer);

// Get a mail session
Session session = Session.getDefaultInstance(props, null);

// Define a new mail message
Message message = new MimeMessage(session);
message.setFrom(new InternetAddress(from));
message.addRecipient(Message.RecipientType.TO, new InternetAddress(to));
message.setSubject(subject);

// Create a message part to represent the body text
BodyPart messageBodyPart = new MimeBodyPart();
messageBodyPart.setText(messageBody);

//use a MimeMultipart as we need to handle the file attachments
Multipart multipart = new MimeMultipart();

//add the message body to the mime message
multipart.addBodyPart(messageBodyPart);

// add any file attachments to the message
addAtachments(attachments, multipart);

// Put all message parts in the message
message.setContent(multipart);

// Send the message
Transport.send(message);

}

protected static void addAtachments(String[] attachments, Multipart multipart)
throws MessagingException, AddressException
{
for(int i = 0; i<= attachments.length -1; i++)
{
String filename = attachments[i];
MimeBodyPart attachmentBodyPart = new MimeBodyPart();

//use a JAF FileDataSource as it does MIME type detection
DataSource source = new FileDataSource(filename);
attachmentBodyPart.setDataHandler(new DataHandler(source));

//assume that the filename you want to send is the same as the
//actual file name - could alter this to remove the file path
attachmentBodyPart.setFileName(filename);

//add the attachment
multipart.addBodyPart(attachmentBodyPart);
}
}

public static void main(String args[]){
try
{
//MailClient client = new MailClient();
String server="smtp.gmail.com";
String from="tavopa7@gmail.com";
String to = "tavopa7@gmail.com";
String subject="Test";
String message="Testing";
String[] filenames =
{"C:/YServer.txt"};

sendMail(server,from,to,subject,message,filenames);
}
catch(Exception e)
{
e.printStackTrace(System.out);
}
System.out.println("Se acabo");

}

}

y este es el error

javax.mail.SendFailedException: Sending failed;
nested exception is:
class javax.mail.MessagingException: Could not connect to SMTP host: smtp.gmail.com, port: 25, response: -1
at javax.mail.Transport.send0(Transport.java:218)
at javax.mail.Transport.send(Transport.java:80)
at mmp.usa.ejb.Mail.sendMail(Mail.java:67)
at mmp.usa.ejb.Mail.main(Mail.java:108)

si alguien me puede ayudar seria magnífico, gracias a todos....