ImapX IndexOutOfRangeException on Message.Process()

private void Start()
        {
            int amountRead = 0;
            failedMessages.Clear();

            foreach(string origin Properties.Settings.Default.MailOrigins)
            {
                IMailOriginAdapter adapter = MailOriginFactory.CreateMailOriginContainer(origin);

                foreach (ImapX.Message message in adapter.Messages())
                {
                    if (SendWebRequest(url))
                    {
                        message.Process();
                        amountRead++;

                        Dispatcher.BeginInvoke(new MethodInvoker(delegate
                        {
                            this.btnStart.Content = "Read [" + amountRead + "/" + GmailUser.Instance.Messages.Count + "]";
                        }));
                    }
                    else
                    {
                        failedMessages.Add(message);
                    }
                }

                System.Windows.MessageBox.Show(adapter.GmailFromEmail() + " reading completed.");
            }
        }

private void worker_DoWork(object sender, DoWorkEventArgs e)
        {
            foreach (Message message in adapter.Messages())
            {
                message.Process();
                worker.ReportProgress(mailsRead);
                mailsRead++;
            }
        }