ActionMailer::DeliveryMethods::ClassMethods

Helpers for creating and wrapping delivery behavior, used by DeliveryMethods.

Methods
A
Instance Public methods
add_delivery_method(symbol, klass, default_options = {})

Adds a new delivery method through the given class using the given symbol as alias and the default options supplied.

add_delivery_method :sendmail, Mail::Sendmail,
  location:  '/usr/sbin/sendmail',
  arguments: '-i'

Source: show | on GitHub 

# File actionmailer/lib/action_mailer/delivery_methods.rb, line 55
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