```ruby
require 'action_mailer'
require 'postmark'
require 'postmark_delivery_method'

module PostmarkInstaller
  extend self
  
  def auto_detect_and_install
    if ActionMailer::Base.respond_to?(:add_delivery_method)
      install_in_rails_3
    else
      install_in_rails_2
    end
  end
  
  def install_in_rails_2
    ActionMailer::Base.send(:include, PostmarkDeliveryMethod)
  end
  
  def install_in_rails_3
    ActionMailer::Base.add_delivery_method :postmark, Mail::Postmark, :api_key => nil
    Mail::Message.send(:include, Postmark::AttachmentsFixForMail)
  end
  
end

PostmarkInstaller.auto_detect_and_install```

Remove attachments fix from the Rails 3 installation process.
user
```ruby
require 'action_mailer'
require 'postmark'
require 'postmark_delivery_method'

module PostmarkInstaller
  extend self

  def auto_detect_and_install
    if ActionMailer::Base.respond_to?(:add_delivery_method)
      install_in_rails_3
    else
      install_in_rails_2
    end
  end

  def install_in_rails_2
    ActionMailer::Base.send(:include, PostmarkDeliveryMethod)
  end

  def install_in_rails_3
    ActionMailer::Base.add_delivery_method :postmark, Mail::Postmark, :api_key => nil
  end

end

PostmarkInstaller.auto_detect_and_install```
assistant