diff --git a/CHANGELOG.md b/CHANGELOG.md
index 345e865..40f491e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,18 @@
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [2.4.5] - 2021.07.09
+
+### Removed
+
+- `Truemail::RegexConstant::REGEX_DOMAIN_FROM_EMAIL`
+
+### Updated
+
+- `Truemail::Validate::Mx`
+- Updated gem development dependencies
+- Updated gem version
+
 ## [2.4.4] - 2021.06.29
 
 ### Updated
diff --git a/Gemfile.lock b/Gemfile.lock
index 3815a69..fe689a5 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,13 +1,13 @@
 PATH
   remote: .
   specs:
-    truemail (2.4.4)
+    truemail (2.4.5)
       simpleidn (~> 0.2.1)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    addressable (2.7.0)
+    addressable (2.8.0)
       public_suffix (>= 2.0.2, < 5.0)
     ast (2.4.2)
     bundler-audit (0.8.0)
@@ -21,7 +21,7 @@ GEM
     crack (0.4.5)
       rexml
     diff-lcs (1.4.4)
-    dns_mock (1.3.0)
+    dns_mock (1.3.1)
     docile (1.4.0)
     faker (2.18.0)
       i18n (>= 1.6, < 2)
@@ -43,7 +43,7 @@ GEM
       iniparse (~> 1.4)
       rexml (~> 3.2)
     parallel (1.20.1)
-    parser (3.0.1.1)
+    parser (3.0.2.0)
       ast (~> 2.4.1)
     pry (0.13.1)
       coderay (~> 1.1)
@@ -54,7 +54,7 @@ GEM
     psych (3.3.2)
     public_suffix (4.0.6)
     rainbow (3.0.0)
-    rake (13.0.3)
+    rake (13.0.6)
     reek (6.0.4)
       kwalify (~> 0.7.0)
       parser (~> 3.0.0)
@@ -75,7 +75,7 @@ GEM
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.10.0)
     rspec-support (3.10.2)
-    rubocop (1.18.0)
+    rubocop (1.18.3)
       parallel (~> 1.10)
       parser (>= 3.0.0.0)
       rainbow (>= 2.2.2, < 4.0)
@@ -86,7 +86,7 @@ GEM
       unicode-display_width (>= 1.4.0, < 3.0)
     rubocop-ast (1.7.0)
       parser (>= 3.0.1.1)
-    rubocop-performance (1.11.3)
+    rubocop-performance (1.11.4)
       rubocop (>= 1.7.0, < 2.0)
       rubocop-ast (>= 0.4.0)
     rubocop-rspec (2.4.0)
@@ -121,19 +121,19 @@ PLATFORMS
   x86_64-darwin-20
 
 DEPENDENCIES
-  bundler (~> 2.2, >= 2.2.21)
+  bundler (~> 2.2, >= 2.2.23)
   bundler-audit (~> 0.8.0)
-  dns_mock (~> 1.3)
+  dns_mock (~> 1.3, >= 1.3.1)
   faker (~> 2.18)
   fasterer (~> 0.9.0)
   json_matchers (~> 0.11.1)
   overcommit (~> 0.58.0)
   pry-byebug (~> 3.9)
-  rake (~> 13.0, >= 13.0.3)
+  rake (~> 13.0, >= 13.0.6)
   reek (~> 6.0, >= 6.0.4)
   rspec (~> 3.10)
-  rubocop (~> 1.18)
-  rubocop-performance (~> 1.11, >= 1.11.3)
+  rubocop (~> 1.18, >= 1.18.3)
+  rubocop-performance (~> 1.11, >= 1.11.4)
   rubocop-rspec (~> 2.4)
   simplecov (~> 0.17.1)
   truemail!
@@ -141,4 +141,4 @@ DEPENDENCIES
   webmock (~> 3.13)
 
 BUNDLED WITH
-   2.2.21
+   2.2.23
diff --git a/lib/truemail/core.rb b/lib/truemail/core.rb
index 004ea13..206d0b1 100644
--- a/lib/truemail/core.rb
+++ b/lib/truemail/core.rb
@@ -22,7 +22,6 @@ module RegexConstant
     REGEX_DOMAIN = /[\p{L}0-9]+([\-.]{1}[\p{L}0-9]+)*\.\p{L}{2,63}/i.freeze
     REGEX_EMAIL_PATTERN = /(?=\A.{6,255}\z)(\A([\p{L}0-9]+[\W\w]*)@(#{REGEX_DOMAIN})\z)/.freeze
     REGEX_DOMAIN_PATTERN = /(?=\A.{4,255}\z)(\A#{REGEX_DOMAIN}\z)/.freeze
-    REGEX_DOMAIN_FROM_EMAIL = /\A.+@(.+)\z/.freeze
     REGEX_SMTP_ERROR_BODY_PATTERN = /(?=.*550)(?=.*(user|account|customer|mailbox)).*/i.freeze
     REGEX_IP_ADDRESS = /((1\d|[1-9]|2[0-4])?\d|25[0-5])(\.\g<1>){3}/.freeze
     REGEX_IP_ADDRESS_PATTERN = /\A#{REGEX_IP_ADDRESS}\z/.freeze
diff --git a/lib/truemail/validate/domain_list_match.rb b/lib/truemail/validate/domain_list_match.rb
index 72c4cc6..e285973 100644
--- a/lib/truemail/validate/domain_list_match.rb
+++ b/lib/truemail/validate/domain_list_match.rb
@@ -15,7 +15,7 @@ def run
       private
 
       def email_domain
-        @email_domain ||= result.email[Truemail::RegexConstant::REGEX_DOMAIN_FROM_EMAIL, 1]
+        @email_domain ||= result.email[Truemail::RegexConstant::REGEX_EMAIL_PATTERN, 3]
       end
 
       def whitelisted_domain?
diff --git a/lib/truemail/validate/mx.rb b/lib/truemail/validate/mx.rb
index cebaa6e..5bddd84 100644
--- a/lib/truemail/validate/mx.rb
+++ b/lib/truemail/validate/mx.rb
@@ -8,7 +8,6 @@ class Mx < Truemail::Validate::Base
 
       def run
         return false unless Truemail::Validate::Regex.check(result)
-        result.domain = result.punycode_email[Truemail::RegexConstant::REGEX_DOMAIN_FROM_EMAIL, 1]
         return true if success(mx_lookup && domain_not_include_null_mx)
         mail_servers.clear && add_error(Truemail::Validate::Mx::ERROR)
         false
@@ -53,7 +52,10 @@ def mail_servers_found?
       end
 
       def domain
-        result.domain
+        @domain ||= begin
+          result.domain = result.email[Truemail::RegexConstant::REGEX_EMAIL_PATTERN, 3]
+          result.punycode_email[Truemail::RegexConstant::REGEX_EMAIL_PATTERN, 3]
+        end
       end
 
       def hosts_from_mx_records?
diff --git a/lib/truemail/version.rb b/lib/truemail/version.rb
index b479e2d..4e8cb4f 100644
--- a/lib/truemail/version.rb
+++ b/lib/truemail/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module Truemail
-  VERSION = '2.4.4'
+  VERSION = '2.4.5'
 end
diff --git a/spec/support/helpers/context_helper.rb b/spec/support/helpers/context_helper.rb
index c3835ce..a52717a 100644
--- a/spec/support/helpers/context_helper.rb
+++ b/spec/support/helpers/context_helper.rb
@@ -18,6 +18,10 @@ def random_uniq_domain_name
       faker.unique.domain_name
     end
 
+    def rdns_lookup_host_address(host_address)
+      host_address.gsub(/(\d+).(\d+).(\d+).(\d+)/, '\4.\3.\2.\1.in-addr.arpa')
+    end
+
     private
 
     def faker
diff --git a/spec/support/helpers/context_helper_spec.rb b/spec/support/helpers/context_helper_spec.rb
index d00c60e..7c0d969 100644
--- a/spec/support/helpers/context_helper_spec.rb
+++ b/spec/support/helpers/context_helper_spec.rb
@@ -30,4 +30,10 @@
       expect(random_ip_address).to match(Truemail::RegexConstant::REGEX_DNS_SERVER_ADDRESS_PATTERN)
     end
   end
+
+  describe '#rdns_lookup_host_address' do
+    specify do
+      expect(rdns_lookup_host_address('10.20.30.40')).to eq('40.30.20.10.in-addr.arpa')
+    end
+  end
 end
diff --git a/spec/truemail/core_spec.rb b/spec/truemail/core_spec.rb
index 5ccbb16..d986ed8 100644
--- a/spec/truemail/core_spec.rb
+++ b/spec/truemail/core_spec.rb
@@ -17,7 +17,6 @@
     specify { expect(described_class).to be_const_defined(:REGEX_DOMAIN) }
     specify { expect(described_class).to be_const_defined(:REGEX_EMAIL_PATTERN) }
     specify { expect(described_class).to be_const_defined(:REGEX_DOMAIN_PATTERN) }
-    specify { expect(described_class).to be_const_defined(:REGEX_DOMAIN_FROM_EMAIL) }
     specify { expect(described_class).to be_const_defined(:REGEX_SMTP_ERROR_BODY_PATTERN) }
     specify { expect(described_class).to be_const_defined(:REGEX_IP_ADDRESS) }
     specify { expect(described_class).to be_const_defined(:REGEX_IP_ADDRESS_PATTERN) }
@@ -140,15 +139,6 @@
     end
   end
 
-  describe 'Truemail::RegexConstant::REGEX_DOMAIN_FROM_EMAIL' do
-    subject(:regex_pattern) { described_class::REGEX_DOMAIN_FROM_EMAIL }
-
-    let(:email) { 'i@domain' }
-
-    specify { expect(regex_pattern.match?(email)).to be(true) }
-    specify { expect(email[regex_pattern, 1]).to eq('domain') }
-  end
-
   describe 'Truemail::RegexConstant::REGEX_SMTP_ERROR_BODY_PATTERN' do
     subject(:regex_pattern) { described_class::REGEX_SMTP_ERROR_BODY_PATTERN }
 
diff --git a/spec/truemail/dns/worker_spec.rb b/spec/truemail/dns/worker_spec.rb
index 1d6221f..11b76fd 100644
--- a/spec/truemail/dns/worker_spec.rb
+++ b/spec/truemail/dns/worker_spec.rb
@@ -89,12 +89,9 @@ def dns_resolver_worker_instance
   end
 
   describe '#ptr_records' do
-    subject(:resolve_ptr_records) { dns_resolver_worker_instance.ptr_records(host_address) }
+    subject(:resolve_ptr_records) { dns_resolver_worker_instance.ptr_records(rdns_lookup_host_address(host_address)) }
 
-    # TODO: change it after update dns_mock
-    # let(:host_address) { random_ip_address }
-    # should works with 42.42.42.42 or 42.42.42.42.in-addr.arpa; request for 42.42.42.42
-    let(:host_address) { '42.42.42.42.in-addr.arpa' }
+    let(:host_address) { random_ip_address }
     let(:ptr_records) { ::Array.new(2) { random_domain_name } }
 
     before { dns_mock_server.assign_mocks(host_address => { ptr: ptr_records }) }
diff --git a/spec/truemail/validate/domain_list_match_spec.rb b/spec/truemail/validate/domain_list_match_spec.rb
index f9fa613..85747a3 100644
--- a/spec/truemail/validate/domain_list_match_spec.rb
+++ b/spec/truemail/validate/domain_list_match_spec.rb
@@ -13,7 +13,7 @@
     subject(:domain_list_match_validator) { described_class.check(result_instance) }
 
     let(:email) { random_email }
-    let(:domain) { email[Truemail::RegexConstant::REGEX_DOMAIN_FROM_EMAIL, 1] }
+    let(:domain) { email[Truemail::RegexConstant::REGEX_EMAIL_PATTERN, 3] }
     let(:configuration_instance) { create_configuration }
     let(:result_instance) { Truemail::Validator::Result.new(email: email, configuration: configuration_instance) }
 
diff --git a/truemail.gemspec b/truemail.gemspec
index 894712f..c6ba7a7 100644
--- a/truemail.gemspec
+++ b/truemail.gemspec
@@ -33,19 +33,19 @@ Gem::Specification.new do |spec|
 
   spec.add_runtime_dependency 'simpleidn', '~> 0.2.1'
 
-  spec.add_development_dependency 'bundler', '~> 2.2', '>= 2.2.21'
+  spec.add_development_dependency 'bundler', '~> 2.2', '>= 2.2.23'
   spec.add_development_dependency 'bundler-audit', '~> 0.8.0'
-  spec.add_development_dependency 'dns_mock', '~> 1.3'
+  spec.add_development_dependency 'dns_mock', '~> 1.3', '>= 1.3.1'
   spec.add_development_dependency 'faker', '~> 2.18'
   spec.add_development_dependency 'fasterer', '~> 0.9.0'
   spec.add_development_dependency 'json_matchers', '~> 0.11.1'
   spec.add_development_dependency 'overcommit', '~> 0.58.0'
   spec.add_development_dependency 'pry-byebug', '~> 3.9'
-  spec.add_development_dependency 'rake', '~> 13.0', '>= 13.0.3'
+  spec.add_development_dependency 'rake', '~> 13.0', '>= 13.0.6'
   spec.add_development_dependency 'reek', '~> 6.0', '>= 6.0.4'
   spec.add_development_dependency 'rspec', '~> 3.10'
-  spec.add_development_dependency 'rubocop', '~> 1.18'
-  spec.add_development_dependency 'rubocop-performance', '~> 1.11', '>= 1.11.3'
+  spec.add_development_dependency 'rubocop', '~> 1.18', '>= 1.18.3'
+  spec.add_development_dependency 'rubocop-performance', '~> 1.11', '>= 1.11.4'
   spec.add_development_dependency 'rubocop-rspec', '~> 2.4'
   spec.add_development_dependency 'simplecov', '~> 0.17.1'
   spec.add_development_dependency 'truemail-rspec', '~> 0.6'