How can i read multiple email accounts?

Question

hi,
my program is to get emails from multiple email accounts, and grab the attachments, but it doesn't work properly.
If there's only one email account, it works fine, but if there are more, it looks like that the program always goes into the first mail account to read the messages. i suspect that the 'Server' or the 'Session' are not reset before each connection, i printed out the connected 'Folder', it looks fine, but every time the 'Folder.getMessageCount()' returns the same number of messages as the first email account has.
Here's my code:
// this is to get the folder, mostly 'inbox'
// serverString is like: "protocol://username@host/foldername"
// all parameters are retrieved from the Database
public static Folder getMailFolder(String serverString, String username, String password) throws Exception {
        // URLName server = new URLName("protocol://username@host/foldername");
        Folder folder = null;
        URLName server = new URLName(serverString);
        // the session is created by grabbing the authentication using the username and password
        // the MailAuthenticator is an inner class as shown at the bottom
        Session session = Session.getDefaultInstance(new Properties(),
                new MailAuthenticator(username, password));
        folder = session.getFolder(server);
        // this message always show the same number of messages
        System.out.println("folder retrieved for " + serverString + ", with " + folder.getMessageCount() + " messages");
        return folder;
// this method is to get the messages from the folder
public static void getEmailWithSubjectContaining(String emailUrl, String username, String password,
              String regex, String filepath, boolean addPrefix, boolean delete)
         throws Exception {
         Folder folder = getMailFolder(emailUrl, username, password);
        if (folder == null)  return;
        folder.open(Folder.READ_WRITE);
        Message[] msgs = folder.getMessages();
        // Here is my problem, the msgs.length always returns the same value
        // which is the number of messages that the first email account has
        System.out.println("Totally there are " + msgs.length);
        for (int i = 0; i < msgs.length; i++) {
             String pathToSave = filepath;
               String subject = msgs.getSubject();
               System.out.println("Email subject: " + subject);
// examine if the message should be dumped and deleted
               if (!subject.matches(regex)) {
                    System.out.println("Email subject doesn't match regex: " + regex + ", this email is ignored.");
                    continue;
               Part p = (Part) msgs[i];
//               p.getFileName();
               if (addPrefix) {
                    pathToSave = filepath + "/" + getFilenamePrefix(subject);
// this method call is to save the attachment
               dumpAttachment(p, pathToSave);
               msgs[i].setFlag(Flags.Flag.DELETED, delete);
          folder.expunge();
folder.close(false);
// this method calls getEmailWithSubjectContaining using a loop
public static void getEmailWithSubjectContaining(String dbUsername, String dbPassword, String dbUrl) throws Exception {
     Connection con = null;
     if (dbUrl == null || dbUrl.equals("")) dbUrl = "jdbc:mysql://localhost/email_util";
          try {
// here is just simply get the Database connection
               con = MySqlJDBCConnection.getConnection(dbUsername, dbPassword, dbUrl);
               Statement s = con.createStatement();
               String sql = "SELECT * FROM email_fetching_config WHERE active = 1";
               ResultSet rs = s.executeQuery(sql);
               while (rs.next()) {
                    String protocol = rs.getString("protocol");
                    String url = rs.getString("url");
                    String box = rs.getString("email_box");
                    String username = rs.getString("username");
                    String password = rs.getString("password");
                    String regex = rs.getString("sub_regex");
                    String path = rs.getString("save_to");
                    String prefix = rs.getString("append_prefix");
                    boolean delete = rs.getBoolean("delete");
                    String emailUrl = protocol + "://" + username + "@" + url + "/" + box;
                    boolean addPrefix = (!prefix.equals("") || prefix != null);
                    System.out.println("Ready to grab emails from " + emailUrl + ", path to save is: " + path);
                    try {
                         getEmailWithSubjectContaining(emailUrl, username, password, regex, path, addPrefix, delete);
                    } catch (Exception ex) {
          } catch (Exception ex) {
               ex.printStackTrace();
          } finally {
               MySqlJDBCConnection.close();
********* Authenticator *******
class MailAuthenticator extends Authenticator {
private String username;
private String password;
public MailAuthenticator() {
public MailAuthenticator(String username, String password) {
this.username = username;
this.password = password;
public PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(this.username, this.password);
This is all my program doing, anyone knows what the program is? thanks for your help!
regards                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           

Answer 1

Assuming you're passing in the right URL, I don't see the problem.
Still, try change session.getDefaultInstance to session.getInstance
and see if that helps. If not, turn on session debugging and check the
protocol trace for clues. If you still can't figure it out, post the protocol
trace.