Ensure.Argument.NotNull(template);
            var asc = UserBase.GetAccountStateCode(template.QueueAccountState);


            var users = _userRepo.AllIncluding(u => u.SentEmails).Where(u => u.AccountStateCode == asc && u is Customer && !u.SentEmails.Select(s => s.EmailTemplateId).Contains(template.Id));
            switch (template.QueueAfter)
            {
                case QueueAfter.RegistrationDate:
                    users = users.Where(ud => ud.RegisteredOn <= DateTime.Today.AddDays(template.QueueDays));
                    break;
                default:
                    throw new ArgumentOutOfRangeException();
            }

            return users
                    .Select(user => user as Customer)
                    .ToList();