Ruby on Rails

I am trying to figure out why this block of code in my environments/production.rb file is causing the dkim signing to break.  I have email being sent from a rake task with my UserMailer class.  It is derived from Devise::Mailer.  If I have the action_mailer configuration block within the "config.after_initialize" the dkim signature does not go through.  If I don't have that line "after_initialize" the signature goes through.  Can someone shed some light on this for me?

Here's the code for my UserMailer class and the production.rb file. 

user_mailer.rb

require "#{Rails.root}/app/helpers/user_helper"
include UserHelper

class UserMailer < Devise::Mailer
  helper :application # gives access to all helpers defined within `application_helper`.
  include Devise::Controllers::UrlHelpers # Optional. eg. `confirmation_url`
  default from: "Save The Sparkles <con...@savethesparkles.com>",
  reply_to: "con...@savethesparkles.com"
  ...
end

environments/production.rb 

config.action_mailer.asset_host     = 'http://savethesparkles.com'

config.action_mailer.default_url_options = { host: 'savethesparkles.com' }
config.after_initialize do
  config.action_mailer.perform_deliveries = true
  config.action_mailer.raise_delivery_errors = true
  config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = {
    address:              'email-smtp.us-east-1.amazonaws.com',
    port:                 587,
    domain:               'savethesparkles.com',
    user_name:            ENV['AWS_SES_USER'],
    password:             ENV['AWS_SES_PASS'],
    authentication:       :login,
    enable_starttls_auto: true
  }
end