diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 5583de5d0..103a53077 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -23,6 +23,8 @@ jobs:
            timeout: 5
          - ruby: '3.0'
            timeout: 5
+         - ruby: 3.1
+           timeout: 5
          - ruby: jruby
            timeout: 5
          - ruby: truffleruby
diff --git a/Gemfile b/Gemfile
index 907cad58c..acbbb81fd 100644
--- a/Gemfile
+++ b/Gemfile
@@ -15,3 +15,9 @@ gem 'mini_mime'
 gem 'byebug', :platforms => :mri
 
 gem "psych", "< 4"
+
+gem "io-wait", ">= 0.1.0.a"
+
+if RUBY_PLATFORM == "java"
+  gem "strscan", github: "https://github.com/ruby/strscan/pull/25"
+end
diff --git a/mail.gemspec b/mail.gemspec
index e36dddc41..5813e2db5 100644
--- a/mail.gemspec
+++ b/mail.gemspec
@@ -16,6 +16,9 @@ Gem::Specification.new do |s|
   s.required_ruby_version = ">= 2.5"
 
   s.add_dependency('mini_mime', '>= 0.1.1')
+  s.add_dependency('net-smtp')
+  s.add_dependency('net-imap')
+  s.add_dependency('net-pop')
 
   s.add_development_dependency('bundler', '>= 1.0.3')
   s.add_development_dependency('rake', '> 0.8.7')