JavaMail not sending SMTP email via postfix

Question

I am trying to set up JavaMail to send and receive emails using Postfix, which is installed on my CentOS7 development box. I have confirmed that postfix is able to display received emails by typing MAIL=/home/root/Maildir into the terminal, followed by return and then mail, which lists all received emails for the user account. But yet when I log in as root and check to see the received emails in the CentOS 7 terminal, there are no new emails after I run my Javamail code as described below. How can I get Javamail to send smtp email?

Here is my class:

import java.util.*;
import javax.mail.*;
import javax.mail.internet.*;
import javax.activation.*;

//Send a simple, single part, text/plain e-mail
public class TestEmail {

  public void send(){
     // SUBSTITUTE YOUR EMAIL ADDRESSES HERE!
     String to = "root@localhost";
     String from = "username@localhost";
     // SUBSTITUTE YOUR ISP'S MAIL SERVER HERE!
     String host = "localhost";

     // Create properties, get Session
     Properties props = new Properties();

     //http://docs.oracle.com/javaee/6/api/javax/mail/Session.html
     // If using static Transport.send(),
     // need to specify which host to send it to
     props.put("mail.smtp.host", host);
     // To see what is going on behind the scene
     props.put("mail.debug", "true");
     Session session = Session.getInstance(props);

     try {
         // Instantiate a message
         Message msg = new MimeMessage(session);

         //Set message attributes
         msg.setFrom(new InternetAddress(from));
         InternetAddress[] address = {new InternetAddress(to)};
         msg.setRecipients(Message.RecipientType.TO, address);
         msg.setSubject("A new record was just added.");
         msg.setSentDate(new Date());

         // Set message content
         msg.setText("This is a test of sending a " +
                     "plain text e-mail through Java.\n" +
                     "Here is line 2.");

         //Send the message
         Transport.send(msg);
     }
     catch (MessagingException mex) {
         // Prints all nested (chained) exceptions as well
         mex.printStackTrace();
     }
 }
}//End of class  

I call the class as follows:

TestEmail em = new TestEmail();
em.send();

The eclipse console produces the following logs when the above code is run:

DEBUG: JavaMail version 1.5.0-b01
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.SMTPSSLTransport,Oracle], com.sun.mail.smtp.SMTPTransport=javax.mail.Provider[TRANSPORT,smtp,com.sun.mail.smtp.SMTPTransport,Oracle], com.sun.mail.imap.IMAPSSLStore=javax.mail.Provider[STORE,imaps,com.sun.mail.imap.IMAPSSLStore,Oracle], com.sun.mail.pop3.POP3SSLStore=javax.mail.Provider[STORE,pop3s,com.sun.mail.pop3.POP3SSLStore,Oracle], com.sun.mail.imap.IMAPStore=javax.mail.Provider[STORE,imap,com.sun.mail.imap.IMAPStore,Oracle], com.sun.mail.pop3.POP3Store=javax.mail.Provider[STORE,pop3,com.sun.mail.pop3.POP3Store,Oracle]}
DEBUG: Providers Listed By Protocol: {imaps=javax.mail.Provider[STORE,imaps,com.sun.mail.imap.IMAPSSLStore,Oracle], imap=javax.mail.Provider[STORE,imap,com.sun.mail.imap.IMAPStore,Oracle], smtps=javax.mail.Provider[TRANSPORT,smtps,com.sun.mail.smtp.SMTPSSLTransport,Oracle], pop3=javax.mail.Provider[STORE,pop3,com.sun.mail.pop3.POP3Store,Oracle], pop3s=javax.mail.Provider[STORE,pop3s,com.sun.mail.pop3.POP3SSLStore,Oracle], smtp=javax.mail.Provider[TRANSPORT,smtp,com.sun.mail.smtp.SMTPTransport,Oracle]}
DEBUG: successfully loaded resource: /META-INF/javamail.default.address.map
DEBUG: getProvider() returning javax.mail.Provider[TRANSPORT,smtp,com.sun.mail.smtp.SMTPTransport,Oracle]
DEBUG SMTP: useEhlo true, useAuth false
DEBUG SMTP: trying to connect to host "localhost", port 25, isSSL false
220 localhost.localdomain ESMTP Postfix
DEBUG SMTP: connected to host "localhost", port: 25

EHLO localhost.localdomain
250-localhost.localdomain
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
DEBUG SMTP: Found extension "PIPELINING", arg ""
DEBUG SMTP: Found extension "SIZE", arg "10240000"
DEBUG SMTP: Found extension "VRFY", arg ""
DEBUG SMTP: Found extension "ETRN", arg ""
DEBUG SMTP: Found extension "ENHANCEDSTATUSCODES", arg ""
DEBUG SMTP: Found extension "8BITMIME", arg ""
DEBUG SMTP: Found extension "DSN", arg ""
DEBUG SMTP: use8bit false
MAIL FROM:<username@localhost>
250 2.1.0 Ok
RCPT TO:<root@localhost>
250 2.1.5 Ok
DEBUG SMTP: Verified Addresses
DEBUG SMTP:   root@localhost
DATA
354 End data with <CR><LF>.<CR><LF>
Date: Mon, 5 Jan 2015 13:12:02 -0800 (PST)
From: username@localhost
To: root@localhost
Message-ID: <[e-mail]>
Subject: A new record was just added.
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit

This is a test of sending a plain text e-mail through Java.
Here is line 2.
.
250 2.0.0 Ok: queued as DB1249A618
QUIT
221 2.0.0 Bye
sessionID is: 0816C244BDBAAD890D82138DC3801962

Solution

from the log Ok: queued as DB1249A618 the mail is correctly recived by SMTP server. so problem may be misconfigured server (maybe an antispam filter) or wrong mail address.

Look here https://serverfault.com/questions/485505/get-postfix-to-forward-roots-mail to check your server configuration is right.