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congrats.rake

namespace :mailers do
  desc 'Send the "congrats" mail'
  task congrats: :environment do
    lists = Photobook.distinct_list_for_date Date.yesterday

    lists.each do |list|
      book = list.most_recent_book

      if book.present?
        mailer = Routines.congrats(book)
        mailer.deliver
      end
    end
  end
end

development.rb

config.action_mailer.delivery_method = :letter_opener
config.action_mailer.default_url_options = {:host => "localhost:3000"}
Rails.application.routes.default_url_options[:host] = 'localhost:3000'

routines.rb

# encoding: utf-8

class Routines < ActionMailer::Base
  layout 'mailer'
  default from: 'someaddr', to: 'anotheraddr'
  add_template_helper ApplicationHelper

  def congrats(photobook)
    @photobook = photobook
    @user = photobook.user
    mail subject: 'test'
  end
end

staging.rb

Rails.application.routes.default_url_options[:host] = "host"
config.action_mailer.default_url_options = {host: 'samehost'}
  config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = {
    # smpt settings here
  }