diff --git a/lib/mailgun-ruby.rb b/lib/mailgun-ruby.rb
index be20eca4..caefcf73 100644
--- a/lib/mailgun-ruby.rb
+++ b/lib/mailgun-ruby.rb
@@ -1,2 +1,2 @@
-require 'mailgun'
-require 'railgun' if defined?(Rails) && defined?(ActionMailer)
+require_relative 'mailgun'
+require_relative 'railgun' if defined?(Rails) && defined?(ActionMailer)
diff --git a/lib/mailgun.rb b/lib/mailgun.rb
index e5eabed4..03d70c79 100644
--- a/lib/mailgun.rb
+++ b/lib/mailgun.rb
@@ -1,25 +1,40 @@
+# require ruby dependencies
+require 'json'
+require 'openssl'
 require 'tempfile'
-require 'faraday'
+require 'time'
+require 'uri'
 require 'yaml'
-require 'json'
 
-require 'mailgun/version'
-require 'mailgun/client'
-require 'mailgun/response'
-require 'mailgun/chains'
-require 'mailgun/address'
-require 'mailgun/lists/opt_in_handler'
-require 'mailgun/messages/batch_message'
-require 'mailgun/messages/message_builder'
-require 'mailgun/events/events'
+# require external dependencies
+require 'faraday'
+require 'faraday/multipart'
+require 'mini_mime'
+require 'zeitwerk'
+
 require 'mailgun/exceptions/exceptions'
-require 'mailgun/domains/domains'
-require 'mailgun/webhooks/webhooks'
-require 'mailgun/templates/templates'
-require 'mailgun/subaccounts/subaccounts'
-require 'mailgun/tags/tags'
-require 'mailgun/metrics/metrics'
-require 'mailgun/logs/logs'
+require 'mailgun/helpers/api_version_checker'
+
+# load zeitwerk
+Zeitwerk::Loader.for_gem.tap do |loader| # rubocop:disable Style/SymbolProc
+  loader.ignore("#{__dir__}/mailgun-ruby.rb")
+  loader.ignore("#{__dir__}/railgun.rb")
+  loader.ignore("#{__dir__}/railgun")
+
+  loader.collapse("#{__dir__}/mailgun/domains")
+  loader.collapse("#{__dir__}/mailgun/events")
+  loader.collapse("#{__dir__}/mailgun/exceptions")
+  loader.collapse("#{__dir__}/mailgun/helpers")
+  loader.collapse("#{__dir__}/mailgun/lists")
+  loader.collapse("#{__dir__}/mailgun/logs")
+  loader.collapse("#{__dir__}/mailgun/messages")
+  loader.collapse("#{__dir__}/mailgun/metrics")
+  loader.collapse("#{__dir__}/mailgun/subaccounts")
+  loader.collapse("#{__dir__}/mailgun/tags")
+  loader.collapse("#{__dir__}/mailgun/templates")
+  loader.collapse("#{__dir__}/mailgun/webhooks")
+  loader.setup
+end
 
 # Module for interacting with the sweet Mailgun API.
 #
diff --git a/lib/mailgun/address.rb b/lib/mailgun/address.rb
index c46be75d..1ea3511b 100644
--- a/lib/mailgun/address.rb
+++ b/lib/mailgun/address.rb
@@ -1,5 +1,3 @@
-require 'mailgun/exceptions/exceptions'
-
 module Mailgun
 
   # Mailgun::Address is a simple interface to the Email Validation API.
diff --git a/lib/mailgun/client.rb b/lib/mailgun/client.rb
index d8e31c57..6cd6d16b 100644
--- a/lib/mailgun/client.rb
+++ b/lib/mailgun/client.rb
@@ -1,7 +1,3 @@
-require 'mailgun/chains'
-require 'mailgun/suppressions'
-require 'mailgun/exceptions/exceptions'
-
 module Mailgun
   # A Mailgun::Client object is used to communicate with the Mailgun API. It is a
   # wrapper around Faraday so you don't have to worry about the HTTP aspect
@@ -32,14 +28,7 @@ def initialize(api_key = Mailgun.api_key,
       }
       request_options.merge!(request: {timeout: timeout}) if timeout
 
-      @http_client =  Faraday.new(request_options) do |conn|
-        conn.request :multipart
-        conn.request :authorization, :basic, 'api', api_key
-        conn.request :url_encoded
-        conn.response :raise_error, include_request: true
-        conn.adapter Faraday.default_adapter
-        conn.options.params_encoder = Faraday::FlatParamsEncoder
-      end
+      @http_client = build_http_client(api_key, request_options)
 
       @test_mode = test_mode
       @api_version = api_version
@@ -262,5 +251,16 @@ def perform_data_validation(working_domain, data)
         working_domain
       ) if message.fetch('from', []).empty? && message.fetch(:from, []).empty?
     end
+
+    def build_http_client(api_key, request_options)
+      Faraday.new(request_options) do |conn|
+        conn.request :multipart
+        conn.request :authorization, :basic, 'api', api_key
+        conn.request :url_encoded
+        conn.response :raise_error, include_request: true
+        conn.adapter Faraday.default_adapter
+        conn.options.params_encoder = Faraday::FlatParamsEncoder
+      end
+    end
   end
 end
diff --git a/lib/mailgun/domains/domains.rb b/lib/mailgun/domains/domains.rb
index 3cd03461..401e125c 100644
--- a/lib/mailgun/domains/domains.rb
+++ b/lib/mailgun/domains/domains.rb
@@ -1,6 +1,3 @@
-require 'mailgun/exceptions/exceptions'
-require 'mailgun/helpers/api_version_checker'
-
 module Mailgun
 
   # A Mailgun::Domains object is a simple CRUD interface to Mailgun Domains.
diff --git a/lib/mailgun/events/events.rb b/lib/mailgun/events/events.rb
index 44558234..b5e4b2c9 100644
--- a/lib/mailgun/events/events.rb
+++ b/lib/mailgun/events/events.rb
@@ -1,5 +1,3 @@
-require 'mailgun/exceptions/exceptions'
-
 module Mailgun
 
   # A Mailgun::Events object makes it really simple to consume
diff --git a/lib/mailgun/lists/opt_in_handler.rb b/lib/mailgun/lists/opt_in_handler.rb
index 21f08e76..e436737e 100644
--- a/lib/mailgun/lists/opt_in_handler.rb
+++ b/lib/mailgun/lists/opt_in_handler.rb
@@ -1,6 +1,3 @@
-require 'uri'
-require 'openssl'
-
 module Mailgun
 
   # Public: Provides methods for creating and handling opt-in URLs,
diff --git a/lib/mailgun/logs/logs.rb b/lib/mailgun/logs/logs.rb
index 7c4e7424..d4d41cc7 100644
--- a/lib/mailgun/logs/logs.rb
+++ b/lib/mailgun/logs/logs.rb
@@ -1,5 +1,3 @@
-require 'mailgun/exceptions/exceptions'
-
 module Mailgun
   # A Mailgun::Logs object is a simple interface to Mailgun Logs.
   # Uses Mailgun
diff --git a/lib/mailgun/messages/batch_message.rb b/lib/mailgun/messages/batch_message.rb
index bb81c56e..dae331e3 100644
--- a/lib/mailgun/messages/batch_message.rb
+++ b/lib/mailgun/messages/batch_message.rb
@@ -1,5 +1,3 @@
-require 'mailgun/messages/message_builder'
-
 module Mailgun
 
   # A Mailgun::BatchMessage object is used to create a valid payload
diff --git a/lib/mailgun/messages/message_builder.rb b/lib/mailgun/messages/message_builder.rb
index 19dccf78..f9efdc6c 100644
--- a/lib/mailgun/messages/message_builder.rb
+++ b/lib/mailgun/messages/message_builder.rb
@@ -1,7 +1,3 @@
-require 'mini_mime'
-require 'time'
-require 'faraday/multipart'
-
 module Mailgun
 
   # A Mailgun::MessageBuilder object is used to create a valid payload
diff --git a/lib/mailgun/metrics/metrics.rb b/lib/mailgun/metrics/metrics.rb
index 6f63e07a..5d3b9c55 100644
--- a/lib/mailgun/metrics/metrics.rb
+++ b/lib/mailgun/metrics/metrics.rb
@@ -1,5 +1,3 @@
-require 'mailgun/exceptions/exceptions'
-
 module Mailgun
   # A Mailgun::Metrics object is a simple interface to Mailgun Metrics.
   # Uses Mailgun
diff --git a/lib/mailgun/subaccounts/subaccounts.rb b/lib/mailgun/subaccounts/subaccounts.rb
index edfcaf73..8ea36d57 100644
--- a/lib/mailgun/subaccounts/subaccounts.rb
+++ b/lib/mailgun/subaccounts/subaccounts.rb
@@ -1,5 +1,3 @@
-require 'mailgun/exceptions/exceptions'
-
 module Mailgun
 
   # A Mailgun::Subaccounts object is a simple CRUD interface to Mailgun Subaccounts.
diff --git a/lib/mailgun/suppressions.rb b/lib/mailgun/suppressions.rb
index 1b8de722..d24078f3 100644
--- a/lib/mailgun/suppressions.rb
+++ b/lib/mailgun/suppressions.rb
@@ -1,7 +1,3 @@
-require 'uri'
-
-require 'mailgun/exceptions/exceptions'
-
 module Mailgun
 
   # The Mailgun::Suppressions object makes it easy to manage "suppressions"
diff --git a/lib/mailgun/tags/tags.rb b/lib/mailgun/tags/tags.rb
index f3af9e7a..1946b9a9 100644
--- a/lib/mailgun/tags/tags.rb
+++ b/lib/mailgun/tags/tags.rb
@@ -1,5 +1,3 @@
-require 'mailgun/exceptions/exceptions'
-
 module Mailgun
 
   # A Mailgun::Tags object is a simple CRUD interface to Mailgun Tags.
diff --git a/lib/mailgun/templates/templates.rb b/lib/mailgun/templates/templates.rb
index 6b3e945a..2b5e50ab 100644
--- a/lib/mailgun/templates/templates.rb
+++ b/lib/mailgun/templates/templates.rb
@@ -1,5 +1,3 @@
-require 'mailgun/exceptions/exceptions'
-
 module Mailgun
 
   # A Mailgun::Templates object is a simple CRUD interface to Mailgun Templates.
diff --git a/lib/railgun.rb b/lib/railgun.rb
index 566dc5d7..800e6fbb 100644
--- a/lib/railgun.rb
+++ b/lib/railgun.rb
@@ -1,8 +1,15 @@
-require 'railgun/railtie'
-require 'railgun/attachment'
-require 'railgun/errors'
-require 'railgun/mailer'
-require 'railgun/message'
+# require ruby dependencies
+require 'json'
+
+# require external dependencies
+require 'action_mailer'
+require 'mail'
+require 'mailgun'
+require 'rails'
 
 module Railgun
+  require_relative 'railgun/attachment'
+  require_relative 'railgun/errors'
+  require_relative 'railgun/mailer'
+  require_relative 'railgun/railtie'
 end
diff --git a/lib/railgun/mailer.rb b/lib/railgun/mailer.rb
index dfc5c471..4cb199d2 100644
--- a/lib/railgun/mailer.rb
+++ b/lib/railgun/mailer.rb
@@ -1,9 +1,3 @@
-require 'action_mailer'
-require 'json'
-require 'mailgun'
-require 'rails'
-require 'railgun/errors'
-
 module Railgun
 
   # Railgun::Mailer is an ActionMailer provider for sending mail through
diff --git a/lib/railgun/message.rb b/lib/railgun/message.rb
deleted file mode 100644
index 721ec974..00000000
--- a/lib/railgun/message.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require 'mail'
-require 'mailgun/messages/message_builder'
-require 'railgun/attachment'
-require 'railgun/errors'
-
-module Mail
-
-  class Message
-
-    # Attributes to hold Mailgun-specific information
-    attr_accessor :mailgun_variables,
-                  :mailgun_options,
-                  :mailgun_recipient_variables,
-                  :mailgun_headers,
-                  :mailgun_template_variables
-
-  end
-end
diff --git a/lib/railgun/railtie.rb b/lib/railgun/railtie.rb
index a8b71078..0c308f73 100644
--- a/lib/railgun/railtie.rb
+++ b/lib/railgun/railtie.rb
@@ -1,8 +1,15 @@
-require 'railgun/mailer'
-
 module Railgun
   class Railtie < ::Rails::Railtie
     ActiveSupport.on_load(:action_mailer) do
+      Mail::Message.class_eval do
+        # Attributes to hold Mailgun-specific information
+        attr_accessor :mailgun_variables,
+                      :mailgun_options,
+                      :mailgun_recipient_variables,
+                      :mailgun_headers,
+                      :mailgun_template_variables
+      end
+
       add_delivery_method :mailgun, Railgun::Mailer
       ActiveSupport.run_load_hooks(:mailgun_mailer, Railgun::Mailer)
     end
diff --git a/mailgun.gemspec b/mailgun.gemspec
index c43ec09a..319e6306 100644
--- a/mailgun.gemspec
+++ b/mailgun.gemspec
@@ -39,5 +39,6 @@ Gem::Specification.new do |spec|
   spec.add_dependency 'mini_mime'
   spec.add_dependency 'faraday', "~> 2.1"
   spec.add_dependency 'faraday-multipart', '~> 1.1.0'
+  spec.add_dependency 'zeitwerk'
 
 end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 60d5e662..6bf53e3f 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,8 +1,3 @@
-require 'rubygems'
-require 'bundler'
-require 'bundler/setup'
-Bundler.setup(:development)
-
 require 'simplecov'
 SimpleCov.start do
   add_filter "/spec/"