public List<string> GetImportableItems(int packageId, int itemTypeId, Type itemType, ResourceGroupInfo group)
        {
            List<string> items = new List<string>();

            // get service id
            int serviceId = PackageController.GetPackageServiceId(packageId, group.GroupName);
            if (serviceId == 0)
                return items;

            // Mail provider
            MailServer mail = new MailServer();
            ServiceProviderProxy.Init(mail, serviceId);

            if (itemType == typeof(MailDomain))
                items.AddRange(mail.GetDomains());

            return items;
        }