diff --git a/lib/net/smtp/auth_cram_md5.rb b/lib/net/smtp/auth_cram_md5.rb
deleted file mode 100644
index 0490cd6..0000000
--- a/lib/net/smtp/auth_cram_md5.rb
+++ /dev/null
@@ -1,48 +0,0 @@
-unless defined? OpenSSL
-  begin
-    require 'digest/md5'
-  rescue LoadError
-  end
-end
-
-class Net::SMTP
-  class AuthCramMD5 < Net::SMTP::Authenticator
-    auth_type :cram_md5
-
-    def auth(user, secret)
-      challenge = continue('AUTH CRAM-MD5')
-      crammed = cram_md5_response(secret, challenge.unpack1('m'))
-      finish(base64_encode("#{user} #{crammed}"))
-    end
-
-    IMASK = 0x36
-    OMASK = 0x5c
-
-    # CRAM-MD5: [RFC2195]
-    def cram_md5_response(secret, challenge)
-      tmp = digest_class::MD5.digest(cram_secret(secret, IMASK) + challenge)
-      digest_class::MD5.hexdigest(cram_secret(secret, OMASK) + tmp)
-    end
-
-    CRAM_BUFSIZE = 64
-
-    def cram_secret(secret, mask)
-      secret = digest_class::MD5.digest(secret) if secret.size > CRAM_BUFSIZE
-      buf = secret.ljust(CRAM_BUFSIZE, "\0")
-      0.upto(buf.size - 1) do |i|
-        buf[i] = (buf[i].ord ^ mask).chr
-      end
-      buf
-    end
-
-    def digest_class
-      @digest_class ||= if defined?(OpenSSL::Digest)
-                          OpenSSL::Digest
-                        elsif defined?(::Digest)
-                          ::Digest
-                        else
-                          raise '"openssl" or "digest" library is required'
-                        end
-    end
-  end
-end
diff --git a/lib/net/smtp/auth_login.rb b/lib/net/smtp/auth_login.rb
deleted file mode 100644
index 545c1f9..0000000
--- a/lib/net/smtp/auth_login.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-class Net::SMTP
-  class AuthLogin < Net::SMTP::Authenticator
-    auth_type :login
-
-    def auth(user, secret)
-      continue('AUTH LOGIN')
-      continue(base64_encode(user))
-      finish(base64_encode(secret))
-    end
-  end
-end
diff --git a/lib/net/smtp/auth_plain.rb b/lib/net/smtp/auth_plain.rb
deleted file mode 100644
index 7fa1198..0000000
--- a/lib/net/smtp/auth_plain.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-class Net::SMTP
-  class AuthPlain < Net::SMTP::Authenticator
-    auth_type :plain
-
-    def auth(user, secret)
-      finish('AUTH PLAIN ' + base64_encode("\0#{user}\0#{secret}"))
-    end
-  end
-end
diff --git a/test/net/smtp/test_smtp.rb b/test/net/smtp/test_smtp.rb
index f7a38b8..d2fd19a 100644
--- a/test/net/smtp/test_smtp.rb
+++ b/test/net/smtp/test_smtp.rb
@@ -530,16 +530,6 @@ def test_start_auth_cram_md5
       assert_raise Net::SMTPAuthenticationError do
         Net::SMTP.start('localhost', port, user: 'account', password: 'password', authtype: :cram_md5){}
       end
-
-      port = fake_server_start(auth: 'CRAM-MD5')
-      smtp = Net::SMTP.new('localhost', port)
-      auth_cram_md5 = Net::SMTP::AuthCramMD5.new(smtp)
-      auth_cram_md5.define_singleton_method(:digest_class) { raise '"openssl" or "digest" library is required' }
-      Net::SMTP::AuthCramMD5.define_singleton_method(:new) { |_| auth_cram_md5 }
-      e = assert_raise RuntimeError do
-        smtp.start(user: 'account', password: 'password', authtype: :cram_md5){}
-      end
-      assert_equal('"openssl" or "digest" library is required', e.message)
     end
 
     def test_start_instance