module ActionMailer::DeliveryMethods::ClassMethods

def add_delivery_method(symbol, klass, default_options={})
  class_attribute(:"#{symbol}_settings") unless respond_to?(:"#{symbol}_settings")
  send(:"#{symbol}_settings=", default_options)
  self.delivery_methods = delivery_methods.merge(symbol.to_sym => klass).freeze
end

def wrap_delivery_behavior(mail, method=nil, options=nil) # :nodoc:
  method ||= self.delivery_method
  mail.delivery_handler = self
  case method
  when NilClass
    raise "Delivery method cannot be nil"
  when Symbol
    if klass = delivery_methods[method]
      mail.delivery_method(klass, (send(:"#{method}_settings") || {}).merge(options || {}))
    else
      raise "Invalid delivery method #{method.inspect}"
    end
  else
    mail.delivery_method(method)
  end
  mail.perform_deliveries    = perform_deliveries
  mail.raise_delivery_errors = raise_delivery_errors
end