From a Java application we can send an email to any recipient on any domain e.g. gmail, yahoomail, etc. The only thing we needed is a valid SMTP .
We can also set the validation of the sender in the application during session initialization, since it isdisabled by default. If a user is sending an email within local network, the sender ID is not required, but to send across over the network, a sender Id must be included in the message header.
Below is an example which shows how to send mail using Java

package com.demo.mail;

 /**
  *Mail API is provided by the JAVA in 
  *
  */
import javax.mail.*;
import javax.mail.internet.*;

 /**
   *Method SendMail for sending mail form one location to another
   *
   */
public class  SendMail 
{    
    public void postMail( String recipients, String subject, String message , String from) throws MessagingException
    {
        /**
          *Properties Of the Mail Header
          *
          */
      Properties props = new Properties();

 
        props.put("mail.smtp.port", "465");
      props.put("mail.smtp.host", "192.168.10.1");
        
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.port", "25");
        props.put("mail.smtp.socketFactory.port", "25");

        props.put("mail.smtp.socketFactory.class",
 "javax.net.ssl.SSLSocketFactory");

 props.put("mail.smtp.socketFactory.fallback", "false");
 props.setProperty("mail.smtp.quitwait", "false");

        /**
          *Session and Authentication Of the Message, by default 
          * Authentication is disabled
          */
 
 Session session = Session.getDefaultInstance(props,
     new javax.mail.Authenticator() 
 {
 protected PasswordAuthentication getPasswordAuthentication()
{
                      return new PasswordAuthentication("username","password");
                 }
});

     Message msg = new MimeMessage(session);
        
        InternetAddress addressFrom = new InternetAddress(from);
     msg.setFrom(addressFrom);
        
     InternetAddress addressTo = new InternetAddress(recipients);
        msg.setRecipient(Message.RecipientType.TO, addressTo);

        /**
          *Message can have multiple parts and also can have attachments
          *
          */
        
     msg.setSubject(subject);
     msg.setContent(message, "text/plain");
        
     Transport.send(msg);
    }
    
    public static void main(String s[])
    {
        SendMail mail=new SendMail();
        try
        {        
            mail.postMail("recipientsmailID","subject","JavaMail hello world example","SendersmailID");            
        }
        catch (Exception e)
        {
              e.printStackTrace();
        }
    }
}