изпращане на java поща от с в прокси сървър

Опитвам се да изпратя имейл с помощта на API за java mail от с в прокси сървър. Кодът е както следва:

import java.security.Security;
import java.util.Date;
import java.util.Properties;
import javax.mail.Authenticator;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.AddressException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;


public class GmailSender {

public static void main(String[] args) throws AddressException, MessagingException {


Security.addProvider(new com.sun.net.ssl.internal.ssl.Provider());
final String SSL_FACTORY = "javax.net.ssl.SSLSocketFactory";
// Get a Properties object
Properties props = System.getProperties();
props.setProperty("proxySet","true");
props.setProperty("socksProxyHost","192.168.1.103");
props.setProperty("socksProxyPort","3128");
props.setProperty("mail.smtp.host", "smtp.gmail.com");
props.setProperty("mail.smtp.socketFactory.class", SSL_FACTORY);
props.setProperty("mail.smtp.socketFactory.fallback", "false");
props.setProperty("mail.smtp.port", "465");

props.setProperty("mail.smtp.socketFactory.port", "465");
props.put("mail.smtp.auth", "true");
props.put("mail.debug", "true");
props.put("mail.store.protocol", "pop3");
props.put("mail.transport.protocol", "smtp");
final String username = "proxy_userName";
final String password = "proxy_password";
Session session = Session.getDefaultInstance(props,
new Authenticator(){
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(username, password);
}});

// -- Create a new message --
Message msg = new MimeMessage(session);

// -- Set the FROM and TO fields --
msg.setFrom(new InternetAddress("[email protected]"));
msg.setRecipients(Message.RecipientType.TO,
InternetAddress.parse("[email protected]",false));
msg.setSubject("Hello");
msg.setText("How are you");
msg.setSentDate(new Date());
Transport.send(msg);
System.out.println("Message sent.");
}
}

когато стартирам този код, се показва следното съобщение.

DEBUG: JavaMail version 1.4.3
DEBUG: successfully loaded resource: /META-INF/javamail.default.providers
DEBUG: Tables of loaded providers
DEBUG: Providers Listed By Class Name: {com.sun.mail.smtp.SMTPSSLTransport=javax.mail.Provider[TRANSPORT,smtps,com.sun.mail.smtp.S    MTPSSLTransport,Sun Microsystems, Inc],  com.sun.mail.smtp.SMTPTransport=javax.mail.Provider[TRANSPORT,smtp,com.sun.mail.smtp.SMTPTr    ansport,Sun Microsystems, Inc],   com.sun.mail.imap.IMAPSSLStore=javax.mail.Provider[STORE,imaps,com.sun.mail.imap.IMAPSSLSto    re,Sun Microsystems, Inc],  com.sun.mail.pop3.POP3SSLStore=javax.mail.Provider[STORE,pop3s,com.sun.mail.pop3.POP3SSLSto    re,Sun Microsystems, Inc],  com.sun.mail.imap.IMAPStore=javax.mail.Provider[STORE,imap,com.sun.mail.imap.IMAPStore,Sun     Microsystems, Inc],  com.sun.mail.pop3.POP3Store=javax.mail.Provider[STORE,pop3,com.sun.mail.pop3.POP3Store,Sun     Microsystems, Inc]}
DEBUG: Providers Listed By Protocol:  {imaps=javax.mail.Provider[STORE,imaps,com.sun.mail.imap.IMAPSSLStore,Sun Microsystems,  Inc], imap=javax.mail.Provider[STORE,imap,com.sun.mail.imap.IMAPStore,Sun Microsystems,  Inc], smtps=javax.mail.Provider[TRANSPORT,smtps,com.sun.mail.smtp.SMTPSSLTransport,Sun  Microsystems, Inc], pop3=javax.mail.Provider[STORE,pop3,com.sun.mail.pop3.POP3Store,Sun  Microsystems, Inc],  pop3s=javax.mail.Provider[STORE,pop3s,com.sun.mail.pop3.POP3SSLStore,Sun Microsystems,  Inc], smtp=javax.mail.Provider[TRANSPORT,smtp,com.sun.mail.smtp.SMTPTransport,Sun  Microsystems, Inc]}
DEBUG: successfully loaded resource: /META-INF/javamail.default.address.map
DEBUG: getProvider() returning   javax.mail.Provider[TRANSPORT,smtp,com.sun.mail.smtp.SMTPTransport,Sun Microsystems, Inc]
DEBUG SMTP: useEhlo true, useAuth true
DEBUG SMTP: useEhlo true, useAuth true
DEBUG SMTP: trying to connect to host "smtp.gmail.com", port 465, isSSL false
Exception in thread "main" javax.mail.MessagingException: Could not connect to SMTP  host: smtp.gmail.com, port: 465;
  nested exception is:
    java.io.IOException: Couldn't connect using unknown socket factory to host, port: smtp.gmail.com, -1; Exception: java.lang.ClassNotFoundException: false
    at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1706)
    at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:525)
    at javax.mail.Service.connect(Service.java:313)
    at javax.mail.Service.connect(Service.java:172)
    at javax.mail.Service.connect(Service.java:121)
    at javax.mail.Transport.send0(Transport.java:190)
    at javax.mail.Transport.send(Transport.java:120)
    at GmailSender.main(GmailSender.java:57)
Caused by: java.io.IOException: Couldn't connect using unknown socket factory to host,  port: smtp.gmail.com, -1; Exception: java.lang.ClassNotFoundException: false
    at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:216)
    at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1672)
    ... 7 more
Caused by: java.lang.ClassNotFoundException: false
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at com.sun.mail.util.SocketFetcher.getSocketFactory(SocketFetcher.java:322)
    at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:187)
    ... 8 more

Възможно е проблемът да се дължи на наличието на прокси сървър. Въпреки това мога да изпращам имейлите, като вляза в gmail, използвайки браузър от със същия прокси сървър.

Моля, предложете защо програмният метод се проваля, а методът на браузъра работи.

Ще съм благодарен за всяка помощ.