Receive email using IMAP

IMAP presents mail messages as entries in a hierarchy of folders, one of which will be an inbox.

Java Mail comes with Provider implementations for POP3 and IMAP, and the secure versions of those as POP3S and IMAPS.

This HowTo connects to a Google Mail account with IMAPS. IMAP protocol is more advanced than POP. With IMAP, you can talk back to the server and sync your changes automatically.

This Howto connects to a server using the IMAPS (Secure, encrypted IMAP) to download messages with or without attachments and save them into files.

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

public class ReceiveMailImap {

  public ReceiveMailImap() {}

  //
  // inspired by :
  // http://www.mikedesjardins.net/content/2008/03/using-javamail-to-read-and-extract/
  //

  public static void doit() throws MessagingException, IOException {
    Folder folder = null;
    Store store = null;
    try {
      Properties props = System.getProperties();
      props.setProperty("mail.store.protocol", "imaps");

      Session session = Session.getDefaultInstance(props, null);
      // session.setDebug(true);
      store = session.getStore("imaps");
      store.connect("imap.gmail.com","myemail@gmail.com", "******");
      folder = store.getFolder("Inbox");
      /* Others GMail folders :
       * [Gmail]/All Mail   This folder contains all of your Gmail messages.
       * [Gmail]/Drafts     Your drafts.
       * [Gmail]/Sent Mail  Messages you sent to other people.
       * [Gmail]/Spam       Messages marked as spam.
       * [Gmail]/Starred    Starred messages.
       * [Gmail]/Trash      Messages deleted from Gmail.
       */
      folder.open(Folder.READ_WRITE);
      Message messages[] = folder.getMessages();
      System.out.println("No of Messages : " + folder.getMessageCount());
      System.out.println("No of Unread Messages : " + folder.getUnreadMessageCount());
      for (int i=0; i < messages.length; ++i) {
        System.out.println("MESSAGE #" + (i + 1) + ":");
        Message msg = messages[i];
        /*
          if we don''t want to fetch messages already processed
          if (!msg.isSet(Flags.Flag.SEEN)) {
             String from = "unknown";
             ...
          }
        */
        String from = "unknown";
        if (msg.getReplyTo().length >= 1) {
          from = msg.getReplyTo()[0].toString();
        }
        else if (msg.getFrom().length >= 1) {
          from = msg.getFrom()[0].toString();
        }
        String subject = msg.getSubject();
        System.out.println("Saving ... " + subject +" " + from);
        // you may want to replace the spaces with "_"
        // the TEMP directory is used to store the files
        String filename = "c:/temp/" +  subject;
        saveParts(msg.getContent(), filename);
        msg.setFlag(Flags.Flag.SEEN,true);
        // to delete the message
        // msg.setFlag(Flags.Flag.DELETED, true);
      }
    }
    finally {
      if (folder != null) { folder.close(true); }
      if (store != null) { store.close(); }
    }
  }

  public static void saveParts(Object content, String filename)
  throws IOException, MessagingException
  {
    OutputStream out = null;
    InputStream in = null;
    try {
      if (content instanceof Multipart) {
        Multipart multi = ((Multipart)content);
        int parts = multi.getCount();
        for (int j=0; j < parts; ++j) {
          MimeBodyPart part = (MimeBodyPart)multi.getBodyPart(j);
          if (part.getContent() instanceof Multipart) {
            // part-within-a-part, do some recursion...
            saveParts(part.getContent(), filename);
          }
          else {
            String extension = "";
            if (part.isMimeType("text/html")) {
              extension = "html";
            }
            else {
              if (part.isMimeType("text/plain")) {
                extension = "txt";
              }
              else {
                //  Try to get the name of the attachment
                extension = part.getDataHandler().getName();
              }
              filename = filename + "." + extension;
              System.out.println("... " + filename);
              out = new FileOutputStream(new File(filename));
              in = part.getInputStream();
              int k;
              while ((k = in.read()) != -1) {
                out.write(k);
              }
            }
          }
        }
      }
    }
    finally {
      if (in != null) { in.close(); }
      if (out != null) { out.flush(); out.close(); }
    }
  }

  public static void main(String args[]) throws Exception {
    ReceiveMailImap.doit();
  }
}

Done! Happy Coding!