public class ReportingService
{
    public ReportingService(ICustomerData customerData, IReportBuilder reportBuilder, IEmailer emailer)
    {
        CustomerData = customerData;
        ReportBuilder = reportBuilder;
        Emailer = emailer;
    }

    public ICustomerData CustomerData { get; private set; }
    public IReportBuilder ReportBuilder { get; private set; }
    public IEmailer Emailer { get; private set; }

    public void RunCustomerReportBatch()
    {
        var customers = CustomerData.GetCustomersForCustomerReport();

        foreach (var customer in customers)
        {
            var report = ReportBuilder.CreateCustomerReport(customer);
            Emailer.Send(report.ToAddress, report.Body);
        }
    }
}