Errno::ECONNREFUSED: 连接被拒绝 - connect(2) for action mailer

我很长时间以来一直在使用 Rails.现在我在 ActionMailer 中遇到了一个小问题.我想在用户注册时发送电子邮件以确认他的注册.我可以在开发模式下发送电子邮件，但在生产模式下不能发送电子邮件.
异常 Errno::ECONNREFUSED: Connection denied - connect(2) 每次调用 deliver 方法时都会出现.
我编写了以下代码.
我的 SMTP 配置看起来:
config.action_mailer.default_url_options = { :host => "localhost:3000" }

I have been working with rails since a long. Now I am facing a small issue in the ActionMailer. I want to send an email when user gets registered to confirm his registration. I am able to send email in the development mode but where as not in the production mode.
the exception Errno::ECONNREFUSED: Connection refused - connect(2) is coming everytime when deliver method is called.
I have written the following code.
My SMTP config looks:
config.action_mailer.default_url_options = { :host => "localhost:3000" }

  config.action_mailer.delivery_method = :smtp
  config.action_mailer.perform_deliveries = true
  config.action_mailer.raise_delivery_errors = true

  config.action_mailer.smtp_settings = {   
    :openssl_verify_mode => OpenSSL::SSL::VERIFY_NONE,      
    :ssl => true,
    :enable_starttls_auto => true,  #this is the important stuff!
    :address        => 'smtp.xxxx.xxx',
    :port           => xxx,
    :domain         => 'xxxxxx',
    :authentication => :plain,
    :user_name      => 'xxxxxxx@xxx.xxx',
    :password       => 'xxxxxxxxx'
  }

在控制器中，我写了以下内容:

In the controller, I have written the following:

def confirm_registration_in_c       
 @user = User.find_by_email(asdf123@gmail.com)
 if @user
      UserMailer.confirm_registration(@user).deliver            
 end
end

在我的 user_mailer.rb 中:

In my user_mailer.rb :

class UserMailer < ActionMailer::Base
  default from: "from@example.com"

  def confirm_registration(user)
   @user = user
   @user_name = @user.name       
   email = @user.email 
   mail(:to => email, :subject => "Reset your password")
  end
end

我可以在本地主机中以开发模式发送电子邮件，但无法在专用服务器中发送电子邮件.
有人可以帮我吗?

I am able to send email in the development mode in my local host, but I am not able to send the email in the dedicated server.
Can anybody help me please?