public static IEnumerable<Customer> GetCustomersForCustomerReport()
{
    // pretend to do data access
    yield return new Customer("mike@mikelair.com");
    yield return new Customer("leo@leofort.com");
    yield return new Customer("yuna@yunacastle.com");
}

public static Report CreateCustomerReport(Customer customer)
{
    return new Report(customer.Email, $"This is the report for {customer.Email}!");
}

public static void SendEmail(string toAddress, string body)
{
    // pretend to send an email here
    Console.Out.WriteLine("Sent Email to: {0}, Body: '{1}'", toAddress, body);
}