/// <summary>
        /// 添加邮箱
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Menu_Add_Click(object sender, EventArgs e)
        {
            AddEmail addemail = new AddEmail();

            addemail.ShowDialog();
            LoadTree();
        }
        /// <summary>
        /// 删除邮箱
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Menu_Update_Click(object sender, EventArgs e)
        {
            var node = TreeView_Email.SelectedNode;

            if (node == null)
            {
                return;
            }
            AddEmail addemail = new AddEmail(node.Text);

            addemail.ShowDialog();
            LoadTree();
        }