function plt_hide_mailflow_menus() {
//Hide the "Mailflow" menu.
remove_menu_page('mailflow');
//Hide the "Mailflow → Mailflow" menu.
remove_submenu_page('mailflow', 'mailflow');
//Hide the "Mailflow → Settings" menu.
remove_submenu_page('mailflow', 'mailflow_settings');
}
add_action('admin_menu', 'plt_hide_mailflow_menus', 11);