use explicit autoloads rather than from paths

Procfile

 web: bundle exec puma -C config/puma.rb
 fast: bundle exec rake postal:fast_server
-worker: bundle exec rake postal:worker
+worker: bundle exec ruby script/worker.rb
 cron: bundle exec rake postal:cron
 smtp: bundle exec rake postal:smtp_server
 requeuer: bundle exec rake postal:requeuer

config/application.rb

@@ -27,7 +27,7 @@ module Postal
     end
     # Include from lib
-    config.eager_load_paths += %W(#{config.root}/lib #{config.root}/app/jobs)
+    config.eager_load_namespaces << Postal
     # Disable field_with_errors
     config.action_view.field_error_proc = Proc.new { |t, i| t }

config/initializers/postal.rb

-require 'postal/error'
+require 'postal'
 require 'postal/message_db/mysql'

lib/postal.rb

+module Postal
+
+  extend ActiveSupport::Autoload
+
+  eager_autoload do
+    autoload :AppLogger
+    autoload :BounceMessage
+    autoload :Config
+    autoload :Countries
+    autoload :DKIMHeader
+    autoload :Error
+    autoload :FastServer
+    autoload :Helpers
+    autoload :HTTP
+    autoload :HTTPSender
+    autoload :Job
+    autoload :LetsEncrypt
+    autoload :MessageDB
+    autoload :MessageInspection
+    autoload :MessageParser
+    autoload :MessageRequeuer
+    autoload :QueryString
+    autoload :RabbitMQ
+    autoload :ReplySeparator
+    autoload :RspecHelpers
+    autoload :SendResult
+    autoload :Sender
+    autoload :SMTPServer
+    autoload :SpamCheck
+    autoload :UserCreator
+    autoload :Version
+    autoload :Worker
+  end
+
+  def self.eager_load!
+    super
+    Postal::MessageDB.eager_load!
+    Postal::FastServer.eager_load!
+    Postal::SMTPServer.eager_load!
+  end
+
+end

lib/postal/fast_server.rb

+module Postal
+  module FastServer
+    extend ActiveSupport::Autoload
+    eager_autoload do
+      autoload :Client
+      autoload :HTTPHeader
+      autoload :HTTPHeaderSet
+      autoload :Interface
+      autoload :Server
+    end
+  end
+end

lib/postal/message_db.rb

+module Postal
+  module MessageDB
+    extend ActiveSupport::Autoload
+    eager_autoload do
+      autoload :Click
+      autoload :Database
+      autoload :Delivery
+      autoload :LiveStats
+      autoload :Load
+      autoload :Message
+      autoload :Migration
+      autoload :Provisioner
+      autoload :Statistics
+      autoload :SuppressionList
+      autoload :Webhooks
+    end
+  end
+end

lib/postal/smtp_server.rb

+module Postal
+  module SMTPServer
+    extend ActiveSupport::Autoload
+    eager_autoload do
+      autoload :Client
+      autoload :Server
+    end
+  end
+end

lib/tasks/postal.rake

 namespace :postal do
-  desc "Start the backend job worker"
-  task :worker => :environment do
-    Postal::Worker.new([:main]).work
-  end
-
   desc "Start the cron worker"
   task :cron => :environment do
     require 'clockwork'

script/worker.rb

+#!/usr/bin/env ruby
+require_relative '../config/environment'
+Postal::Worker.new([:main]).work