diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
new file mode 100644
index 0000000..122f0f1
--- /dev/null
+++ b/.github/workflows/main.yml
@@ -0,0 +1,28 @@
+name: Ruby
+
+on:
+  push:
+    branches:
+      - main
+
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    name: Ruby ${{ matrix.ruby }}
+    strategy:
+      matrix:
+        ruby:
+          - '3.2'
+          - '3.3'
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby }}
+        bundler-cache: true
+    - name: Run the default task
+      run: bundle exec rake
diff --git a/.ruby-version b/.ruby-version
deleted file mode 100644
index 2bf1c1c..0000000
--- a/.ruby-version
+++ /dev/null
@@ -1 +0,0 @@
-2.3.1
diff --git a/Appraisals b/Appraisals
deleted file mode 100644
index f72605b..0000000
--- a/Appraisals
+++ /dev/null
@@ -1,7 +0,0 @@
-appraise "mail-2.6" do
-  gem "mail", "~> 2.6.0"
-end
-
-appraise "mail-2.7" do
-  gem "mail", "~> 2.7.0"
-end
diff --git a/Gemfile b/Gemfile
index 57bf7b3..d78b22a 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,4 +1,9 @@
 source 'https://rubygems.org'
 
+group :development do
+  gem 'irb'
+  gem 'debug'
+end
+
 # Specify your gem's dependencies in mail-x_smtpapi.gemspec
 gemspec
diff --git a/circle.yml b/circle.yml
deleted file mode 100644
index 6da4746..0000000
--- a/circle.yml
+++ /dev/null
@@ -1,10 +0,0 @@
-machine:
-  ruby:
-    version: 2.3.1
-
-dependencies:
-  post:
-    - bundle exec appraisal install
-test:
-  override:
-    - bundle exec appraisal rake test
diff --git a/gemfiles/mail_2.6.gemfile b/gemfiles/mail_2.6.gemfile
deleted file mode 100644
index ffa830e..0000000
--- a/gemfiles/mail_2.6.gemfile
+++ /dev/null
@@ -1,7 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "mail", "~> 2.6.0"
-
-gemspec path: "../"
diff --git a/gemfiles/mail_2.6.gemfile.lock b/gemfiles/mail_2.6.gemfile.lock
deleted file mode 100644
index 444dab5..0000000
--- a/gemfiles/mail_2.6.gemfile.lock
+++ /dev/null
@@ -1,35 +0,0 @@
-PATH
-  remote: ..
-  specs:
-    mail-x_smtpapi (1.1.0)
-      mail (> 2.6.0)
-
-GEM
-  remote: https://rubygems.org/
-  specs:
-    appraisal (2.2.0)
-      bundler
-      rake
-      thor (>= 0.14.0)
-    mail (2.6.6)
-      mime-types (>= 1.16, < 4)
-    mime-types (3.1)
-      mime-types-data (~> 3.2015)
-    mime-types-data (3.2016.0521)
-    minitest (5.10.3)
-    rake (10.5.0)
-    thor (0.20.0)
-
-PLATFORMS
-  ruby
-
-DEPENDENCIES
-  appraisal
-  bundler (~> 1.7)
-  mail (~> 2.6.0)
-  mail-x_smtpapi!
-  minitest
-  rake (~> 10.0)
-
-BUNDLED WITH
-   1.16.0
diff --git a/gemfiles/mail_2.7.gemfile b/gemfiles/mail_2.7.gemfile
deleted file mode 100644
index e9a4b2f..0000000
--- a/gemfiles/mail_2.7.gemfile
+++ /dev/null
@@ -1,7 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "mail", "~> 2.7.0"
-
-gemspec path: "../"
diff --git a/gemfiles/mail_2.7.gemfile.lock b/gemfiles/mail_2.7.gemfile.lock
deleted file mode 100644
index 0232135..0000000
--- a/gemfiles/mail_2.7.gemfile.lock
+++ /dev/null
@@ -1,33 +0,0 @@
-PATH
-  remote: ..
-  specs:
-    mail-x_smtpapi (1.1.0)
-      mail (> 2.6.0)
-
-GEM
-  remote: https://rubygems.org/
-  specs:
-    appraisal (2.2.0)
-      bundler
-      rake
-      thor (>= 0.14.0)
-    mail (2.7.0)
-      mini_mime (>= 0.1.1)
-    mini_mime (1.0.0)
-    minitest (5.10.3)
-    rake (10.5.0)
-    thor (0.20.0)
-
-PLATFORMS
-  ruby
-
-DEPENDENCIES
-  appraisal
-  bundler (~> 1.7)
-  mail (~> 2.7.0)
-  mail-x_smtpapi!
-  minitest
-  rake (~> 10.0)
-
-BUNDLED WITH
-   1.16.0
diff --git a/mail-x_smtpapi.gemspec b/mail-x_smtpapi.gemspec
index 790e57e..03b9020 100644
--- a/mail-x_smtpapi.gemspec
+++ b/mail-x_smtpapi.gemspec
@@ -17,10 +17,10 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ["lib"]
 
-  spec.add_development_dependency "bundler", "~> 1.7"
-  spec.add_development_dependency "rake", "~> 10.0"
-  spec.add_development_dependency "minitest"
-  spec.add_development_dependency "appraisal"
+  spec.add_development_dependency "bundler", ">= 2.2.3"
+  spec.add_development_dependency "rake", "~> 13.1"
+  spec.add_development_dependency "minitest", "~> 5.21"
 
-  spec.add_dependency "mail", "> 2.6.0"
+  spec.add_dependency "mail", "~> 2.7.1"
+  spec.add_dependency "net-smtp"
 end