Handle EML file with JavaMail

1. Loading an .EML file

When saving an email to a file, the resulting file has an eml extension (email files–which are in RFC 822 format). This kind of file can be read and parsed by JavaMail.

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

public class ReadEmail {

   public static void main(String args[]) throws Exception{
       display(new File("C:\\temp\\message.eml"));

   }

   public static void display(File emlFile) throws Exception{
        Properties props = System.getProperties();
        props.put("mail.host", "smtp.dummydomain.com");
        props.put("mail.transport.protocol", "smtp");

        Session mailSession = Session.getDefaultInstance(props, null);
        InputStream source = new FileInputStream(emlFile);
        MimeMessage message = new MimeMessage(mailSession, source);


        System.out.println("Subject : " + message.getSubject());
        System.out.println("From : " + message.getFrom()[0]);
        System.out.println("--------------");
        System.out.println("Body : " +  message.getContent());
    }
}

A typical eml looks like this:

X-Mozilla-Status: 0001
X-Mozilla-Status2: 00000000
Received: from tomts25-srv.bellnexxia.net
        (tomts25.bellnexxia.net [209.226.175.188])
    by tactika.com (8.9.3/8.9.3) with ESMTP id NAA07621
    for <real@rgagnon.com>; Sun, 1 Feb 2004 13:25:33 -0500 (EST)
Date: Sun, 01 Feb 2004 13:31:40 -0500
From: real gagnon <real@rgagnon.com>
Reply-To: real@rgagnon.com
User-Agent: Mozilla/5.0
   (Windows; U; Windows NT 5.1; en-US; rv:1.4)
   Gecko/20030624 Netscape/7.1 (ax)
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: real@rgagnon.com
Subject: Example for HowTo
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
X-UIDL: oP#!!c]^!!1;-!!T@1"!

Running the above HowTo gives this output:

Subject : Example for HowTo
From : real gagnon <real@rgagnon.com>
--------------
Body :
This is an example for HowTo

2. Saving an email to .EML file

First you connect to the mail server with POP3 or IMAP protocol to retrieve the emails.

 ...
      folder = store.getDefaultFolder().getFolder("INBOX");
      folder.open(Folder.READ_ONLY);
      Message[] messages = folder.getMessages();
      ...
      for (int i=0; i < messages.length; ++i) {
        Message msg = messages[i];
        String subject = msg.getSubject();
        processSaveToFile(msg, subject);
        ...
      }
      ...

Individual email are represented by the Message class.

private void processSaveToFile (javax.mail.Message msg, String subject)
   throws MessagingException, IOException
 {
   String whereToSave = "c:/temp/ + sanitizeFilename(subject) + ".eml";
   logger.info("Sauvegarde vers "+ whereToSave);
   OutputStream out = new FileOutputStream(new File(whereToSave));
   try {
       msg.writeTo(out);
   }
   finally {
       if (out != null) { out.flush(); out.close(); }
   }
 }

Since the subject is used to set the filename, it’s not a bad idea to sanitize it to remove illegal characters.

private static String sanitizeFilename(String name) {
   return name.replaceAll("[:\\\\/*?|<> \"]", "_");
}

Done! Happy Coding!