ActionMailer supports three callbacks
Provide these in your Mailer class
class UserMailer < ApplicationMailer
  after_action :set_delivery_options, :prevent_delivery_to_guests, :set_business_headers
Then create these methods under the private keyword
private
  def set_delivery_options
  end
  def prevent_delivery_to_guests
  end
  def set_business_headers
  end
end