diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 0a3168489..7eb3846e8 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -10,40 +10,39 @@ on:
 jobs:
   ruby:
     name: ${{ matrix.ruby }} (timeout ${{ matrix.timeout }})
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     timeout-minutes: ${{ matrix.timeout }}
     strategy:
       fail-fast: false
       matrix:
        include:
-         - ruby: 2.5
-           timeout: 5
-         - ruby: 2.6
-           timeout: 5
-         - ruby: 2.7
-           timeout: 5
-         - ruby: '3.0'
-           timeout: 5
          - ruby: 3.1
            timeout: 5
+           os: ubuntu-latest
          - ruby: 3.2
            timeout: 5
+           os: ubuntu-latest
          - ruby: 3.3
            timeout: 5
+           os: ubuntu-latest
+         - ruby: ruby
+           timeout: 5
+           os: ubuntu-latest
+         - ruby: head
+           timeout: 5
+           os: ubuntu-latest
          - ruby: truffleruby
            timeout: 50
+           os: ubuntu-latest
          - ruby: truffleruby-head
            timeout: 50
+           os: ubuntu-latest
          - ruby: jruby
            timeout: 5
+           os: ubuntu-22.04
          - ruby: jruby-head
            timeout: 5
-         - ruby: jruby-9.4
-           timeout: 5
-         - ruby: jruby-9.3
-           timeout: 5
-         - ruby: jruby-9.2
-           timeout: 5
+           os: ubuntu-22.04
     steps:
     - name: Installing libyaml-dev
       run: |
diff --git a/Gemfile b/Gemfile
index aaed6fd11..9c20fbb06 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,11 +3,7 @@ source 'https://rubygems.org'
 gemspec
 
 if ENV['MBCHARS'] # see spec/environment.rb
-  if RUBY_VERSION < '2.7.0'
-    gem 'activesupport', '< 6'
-  else
-    gem 'activesupport', :git => 'https://github.com/rails/rails', :branch => 'main'
-  end
+  gem 'activesupport', :git => 'https://github.com/rails/rails', :branch => 'main'
 end
 
 gem 'jruby-openssl', :platforms => :jruby
@@ -15,3 +11,5 @@ gem 'jruby-openssl', :platforms => :jruby
 gem 'mini_mime'
 
 gem 'byebug', :platforms => :mri
+
+gem "benchmark"
diff --git a/README.md b/README.md
index dd0237501..c5653ed97 100644
--- a/README.md
+++ b/README.md
@@ -49,19 +49,9 @@ our documentation, add new features—up to you! Thank you for pitching in.
 
 Mail is tested against:
 
-* Ruby: 2.5
-* Ruby: 2.6
-* Ruby: 2.7
-* Ruby: 3.0
-* Ruby: 3.1
-* Ruby: 3.2
-* JRuby: 9.2
-* JRuby: 9.3
-* JRuby: 9.4
-* JRuby: stable
-* JRuby: head
-* Truffleruby: stable
-* Truffleruby: head
+* Ruby: 3.1, 3.2, 3.3, stable, head
+* JRuby: stable, head
+* Truffleruby: stable, head
 
 As new versions of Ruby are released, Mail will be compatible with support for the "preview" and all "normal maintenance", "security maintenance" and the two most recent "end of life" versions listed at the [Ruby Maintenance Branches](https://www.ruby-lang.org/en/downloads/branches/) page.  Pull requests to assist in adding support for new preview releases are more than welcome.
 
diff --git a/mail.gemspec b/mail.gemspec
index e667f80cd..47b51ed15 100644
--- a/mail.gemspec
+++ b/mail.gemspec
@@ -13,7 +13,7 @@ Gem::Specification.new do |s|
   s.extra_rdoc_files = %w[ README.md ]
   s.rdoc_options << '--exclude' << 'lib/mail/values/unicode_tables.dat'
 
-  s.required_ruby_version = ">= 2.5"
+  s.required_ruby_version = ">= 3.1"
 
   s.add_dependency('logger')
   s.add_dependency('mini_mime', '>= 0.1.1')