@Override
    public void authenticate(String username, String password) throws UnauthorizedException {
        if (username == null || password == null) {
            throw new UnauthorizedException();
        }
        if (username.contains("@")) {
            // Check that the specified domain matches the server's domain
            int index = username.indexOf("@");
            String domain = username.substring(index + 1);
            if (domain.equals(XMPPServer.getInstance().getServerInfo().getXMPPDomain())) {
                username = username.substring(0, index);
            }
        } else {
            // Unknown domain. Return authentication failed.
            throw new UnauthorizedException();
        }

        Log.debug("POP3AuthProvider.authenticate("+username+", ******)");

            // If cache is enabled, see if the auth is in cache.
            if (authCache != null && authCache.containsKey(username)) {
                String hash = authCache.get(username);
                if (StringUtils.hash(password).equals(hash)) {
                    return;
                }
            }

        Properties mailProps = new Properties();
        mailProps.setProperty("mail.debug", String.valueOf(debugEnabled));
        Session session = Session.getInstance(mailProps, null);
        Store store;
        try {
            store = session.getStore(useSSL ? "pop3s" : "pop3");
        }
        catch(NoSuchProviderException e) {
            Log.error(e.getMessage(), e);
            throw new UnauthorizedException(e);
        }

        try {
            if (authRequiresDomain) {
                store.connect(host, port, username + "@" + domain, password);
            }
            else {
                store.connect(host, port, username, password);
            }
        }
        catch(Exception e) {
            Log.error(e.getMessage(), e);
            throw new UnauthorizedException(e);
        }

        if (! store.isConnected()) {
            throw new UnauthorizedException("Could not authenticate user");
        }

        try {
            store.close();
        }
        catch (Exception e) {
            // Ignore.
        }

        // If cache is enabled, add the item to cache.
        if (authCache != null) {
            authCache.put(username, StringUtils.hash(password));
        }

        // See if the user exists in the database. If not, automatically create them.
        UserManager userManager = UserManager.getInstance();
        try {
            userManager.getUser(username);
        }
        catch (UserNotFoundException unfe) {
            String email = username + "@" + (domain!=null?domain:host);
            try {
                Log.debug("POP3AuthProvider: Automatically creating new user account for " + username);
                // Create user; use a random password for better safety in the future.
                // Note that we have to go to the user provider directly -- because the
                // provider is read-only, UserManager will usually deny access to createUser.
                UserManager.getUserProvider().createUser(username, StringUtils.randomString(8),
                        null, email);
            }
            catch (UserAlreadyExistsException uaee) {
                // Ignore.
            }
        }
    }
Initialiazes the POP3AuthProvider with values from the global config file.
xmppserver/src/main/java/org/jivesoftware/openfire/auth/POP3AuthProvider.java