diff --git a/Gemfile b/Gemfile
index 8d77792..bcced19 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,4 +1,4 @@
 # frozen_string_literal: true
 # A sample Gemfile
 source "https://rubygems.org"
-gem 'actionmailer', '3.2.14'
+gem 'actionmailer', '4.0.0'