Java Mail Interview Questions and Answers

Question: Sample code to send email using GMAIL SMTP.

Answer: Here are two examples to show you how to use JavaMail API method to send an email via Gmail SMTP server, using both TLS and SSL connection.

To run this example, you need two dependency libraries – javaee.jar and mail.jar, both are bundle in JavaEE SDK.

Outgoing Mail (SMTP) Server
requires TLS or SSL: smtp.gmail.com (use authentication)
Use Authentication: Yes
Port for TLS/STARTTLS: 587
Port for SSL: 465

GMail SMTP detail here – http://mail.google.com/support/bin/answer.py?hl=en&answer=13287

Send an Email via Gmail SMTP server using TLS connection:

package com.withoutbook.common;

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 SendMailTLS {

public static void main(String[] args) {

final String username = "username@gmail.com";
final String password = "password";

Properties props = new Properties();
props.put("mail.smtp.auth", "true");
props.put("mail.smtp.starttls.enable", "true");
props.put("mail.smtp.host", "smtp.gmail.com");
props.put("mail.smtp.port", "587");

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

try {

Message message = new MimeMessage(session);
message.setFrom(new InternetAddress("from-email@gmail.com"));
message.setRecipients(Message.RecipientType.TO,
InternetAddress.parse("to-email@gmail.com"));
message.setSubject("Testing Subject");
message.setText("Dear Mail Crawler,"
+ "nn No spam to my email, please!");

Transport.send(message);

System.out.println("Done");

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



Send an Email via Gmail SMTP server using SSL connection:

package com.withoutbook.common;

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 SendMailSSL {
public static void main(String[] args) {
Properties props = new Properties();
props.put("mail.smtp.host", "smtp.gmail.com");
props.put("mail.smtp.socketFactory.port", "465");
props.put("mail.smtp.socketFactory.class",
"javax.net.ssl.SSLSocketFactory");
props.put("mail.smtp.auth", "true");
props.put("mail.smtp.port", "465");

Session session = Session.getDefaultInstance(props,
new javax.mail.Authenticator() {
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication("username","password");
}
});

try {

Message message = new MimeMessage(session);
message.setFrom(new InternetAddress("from@no-spam.com"));
message.setRecipients(Message.RecipientType.TO,
InternetAddress.parse("to@no-spam.com"));
message.setSubject("Testing Subject");
message.setText("Dear Mail Crawler," +
"nn No spam to my email, please!");

Transport.send(message);

System.out.println("Done");

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


Exception like:

java.net.UnknownHostException: smtp.gmail.com
Some hit the UnknownHostException: smtp.gmail.com, try ping smtp.gmail.com and make sure you got a response (able to access). Often times, your connection may block by your firewall or proxy behind.