Receive email using POP3Tag(s): Networking


POP3 supports simple download-and-delete requirements for access to remote mailboxes.

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 server using the POP3S (Secure, encrypted POP3) 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.MimeBodyPart;

public class ReceiveMailPOP3 {
  private static final String HOST = "pop.gmail.com";
  private static final String USERNAME = "myemail@gmail.com";
  private static final String PASSWORD = "******";

  public static void doit() throws MessagingException, IOException {
    Folder folder = null;
    Store store = null;
    try {
      Properties props = new Properties();
      props.put("mail.store.protocol", "pop3s"); // Google uses POP3S not POP3
      Session session = Session.getDefaultInstance(props);
      // session.setDebug(true);
      store = session.getStore();
      store.connect(HOST, USERNAME, PASSWORD);
      folder = store.getDefaultFolder().getFolder("INBOX");
      folder.open(Folder.READ_ONLY);
      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];
        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 files will be saved into the TEMP directory
        String filename = "c:/temp/" +  subject;
        saveParts(msg.getContent(), filename);
      }
    }
    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 {
    ReceiveMailPOP3.doit();
  }
}
See this HowTo to download using the IMAP protocol.
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