我正在尝试让ActionMailer发送一封带有Letter_Opener gem的电子邮件。当我尝试使用localhost:3000/mailer/order_mailer查看预览时，终端记录了此错误：

app/mailers/order_mailer.rb:10:in `new_order_email'
Started GET "/rails/mailers/order_mailer/new_order_email" for ::1 at 2023-01-27 16:27:38 -0800
Processing by Rails::MailersController#preview as HTML
  Parameters: {"path"=>"order_mailer/new_order_email"}
OrderMailer#new_order_email: processed outbound mail in 1.2ms
Completed 500 Internal Server Error in 24ms (Allocations: 9119)
  
ActionView::MissingTemplate (Missing template order_mailer/new_order_email with "mailer".

Searched in:
  * "order_mailer"
):

应用程序/邮件程序/订单邮件程序.rb：

class OrderMailer < ApplicationMailer
  default from: 'actionMailerTester2301@gmail.com'

  # layout "order_mailer"
  
  def new_order_email
    @email = 'joeDANE@example.com'

    mail(to: @email, subject: "Thank you for your donation.")

  end
end

在浏览器上，mail(to:.....行被指出，我已经查看了多个stackoverflow条目，但我无法理解它，尽管我认为这是因为我对Ruby不熟悉，不打算理解这个问题。
我希望如果我能找出为什么预览不工作，我会找出与开信宝石的次要问题。