import java.util.Properties;

import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class SendHTMLEmail {
   public static void main(String[] args) {
     //Recipient's email ID needs to be mentioned.
      String to = "宛先アドレス";

     //Sender's email ID needs to be mentioned
      String from = "送信者アドレス";
      final String username = "ユーザー名";//change accordingly
      final String password = "パスワード";//change accordingly

     //Assuming you are sending email through relay.jangosmtp.net
      String host = "ホスト名";

      Properties props = new Properties();
      props.put("mail.smtp.auth", "true");
      props.put("mail.smtp.starttls.enable", "true");
      props.put("mail.smtp.host", host);
      props.put("mail.smtp.port", "ポート番号");

     //Get the Session object.
      Session session = Session.getInstance(props,
         new javax.mail.Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
               return new PasswordAuthentication(username, password);
            }
    });

      try {
           //Create a default MimeMessage object.
            Message message = new MimeMessage(session);

      //Set From: header field of the header.
       message.setFrom(new InternetAddress(from));

      //Set To: header field of the header.
       message.setRecipients(Message.RecipientType.TO,
              InternetAddress.parse(to));

      //Set Subject: header field
       message.setSubject("Testing Subject");

      //Send the actual HTML message, as big as you like
       message.setContent(
              "<h1>This is actual message embedded in HTML tags</h1>",
             "text/html");

      //Send message
       Transport.send(message);

       System.out.println("Sent message successfully....");

      } catch (MessagingException e) {
       e.printStackTrace();
       throw new RuntimeException(e);
      }
   }
}