diff --git a/.reek.yml b/.reek.yml
index 279076f..e86dbd5 100644
--- a/.reek.yml
+++ b/.reek.yml
@@ -33,3 +33,4 @@ detectors:
   FeatureEnvy:
     exclude:
       - Truemail::Validate::Smtp#not_includes_user_not_found_errors
+      - Truemail::GenerateEmailHelper#prepare_user_name
diff --git a/Gemfile.lock b/Gemfile.lock
index caee75f..9cdda17 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    truemail (0.1.2)
+    truemail (0.1.3)
 
 GEM
   remote: https://rubygems.org/
diff --git a/lib/truemail/configuration.rb b/lib/truemail/configuration.rb
index 0a038d7..8a54581 100644
--- a/lib/truemail/configuration.rb
+++ b/lib/truemail/configuration.rb
@@ -29,13 +29,13 @@ def email_pattern=(regex_pattern)
 
     def verifier_email=(email)
       validate_arguments(email, __method__)
-      @verifier_email = email
+      @verifier_email = email.downcase
       default_verifier_domain
     end
 
     def verifier_domain=(domain)
       validate_arguments(domain, __method__)
-      @verifier_domain = domain
+      @verifier_domain = domain.downcase
     end
 
     %i[connection_timeout response_timeout].each do |method|
diff --git a/lib/truemail/core.rb b/lib/truemail/core.rb
index 14c387d..07f3bb2 100644
--- a/lib/truemail/core.rb
+++ b/lib/truemail/core.rb
@@ -10,9 +10,10 @@ def initialize(current_param, class_name)
   end
 
   module RegexConstant
-    REGEX_DOMAIN = /[a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.[a-z]{2,7}/
-    REGEX_EMAIL_PATTERN = /(?=\A.{6,255}\z)(\A([\w|\-|\.]+)@(#{REGEX_DOMAIN})\z)/
+    REGEX_DOMAIN = /[a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.[a-z]{2,63}/i
+    REGEX_EMAIL_PATTERN = /(?=\A.{6,255}\z)(\A([a-zA-Z0-9]+[\w|\-|\.|\+]*)@(#{REGEX_DOMAIN})\z)/
     REGEX_DOMAIN_PATTERN = /(?=\A.{4,255}\z)(\A#{REGEX_DOMAIN}\z)/
+    REGEX_DOMAIN_FROM_EMAIL = /\A.+@(.+)\z/
   end
 
   module Validate
diff --git a/lib/truemail/validate/mx.rb b/lib/truemail/validate/mx.rb
index ef7040b..712d936 100644
--- a/lib/truemail/validate/mx.rb
+++ b/lib/truemail/validate/mx.rb
@@ -9,7 +9,7 @@ class Mx < Truemail::Validate::Base
 
       def run
         return false unless Truemail::Validate::Regex.check(result)
-        result.domain = result.email[Truemail::RegexConstant::REGEX_EMAIL_PATTERN, 3]
+        result.domain = result.email[Truemail::RegexConstant::REGEX_DOMAIN_FROM_EMAIL, 1]
         return true if success(!result.mail_servers.push(*mx_records).empty?)
         add_error(Truemail::Validate::Mx::ERROR)
         false
diff --git a/lib/truemail/validator.rb b/lib/truemail/validator.rb
index 02398f3..bea0fa7 100644
--- a/lib/truemail/validator.rb
+++ b/lib/truemail/validator.rb
@@ -17,7 +17,7 @@ def initialize(errors: {}, mail_servers: [], **args)
     def initialize(email, with: :smtp)
       raise ArgumentError.new(with, :argument) unless VALIDATION_TYPES.include?(with)
       @validation_type = select_validation_type(email, with)
-      @result = Result.new(email: email)
+      @result = Truemail::Validator::Result.new(email: email)
     end
 
     def run
diff --git a/lib/truemail/version.rb b/lib/truemail/version.rb
index 363cddd..90f7614 100644
--- a/lib/truemail/version.rb
+++ b/lib/truemail/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module Truemail
-  VERSION = '0.1.2'
+  VERSION = '0.1.3'
 end
diff --git a/spec/support/helpers/generate_email_helper.rb b/spec/support/helpers/generate_email_helper.rb
index 62f2514..695f887 100644
--- a/spec/support/helpers/generate_email_helper.rb
+++ b/spec/support/helpers/generate_email_helper.rb
@@ -6,7 +6,7 @@ def self.call(**options)
       new(options).call
     end
 
-    def initialize(size: :auto, symbols: %w[- _ .], invalid_email_with: [])
+    def initialize(size: :auto, symbols: %w[- _ . +], invalid_email_with: [])
       @size = calculate_email_size(size)
       @symbols = symbols
       @invalid_symbols = invalid_email_with
@@ -23,7 +23,7 @@ def call
 
     def calculate_email_size(size)
       case size
-      when :auto then rand(10..250)
+      when :auto then rand(15..250)
       when :min then 1
       when :max then 250
       when :out_of_range then rand(251..300)
@@ -36,15 +36,34 @@ def sample_size
       size < (symbols_size + invalid_symbols_size + 1) ? 1 : size - symbols_size - invalid_symbols_size - 1
     end
 
+    def invalid_symbols_empty?
+      invalid_symbols.empty?
+    end
+
+    def size_one?
+      size == 1
+    end
+
     def user_name
       @user_name ||=
-        if size == 1 && !invalid_symbols.empty?
+        if size_one? && !invalid_symbols_empty?
           invalid_symbols.sample
+        elsif size_one? && invalid_symbols_empty?
+          ('a'..'z').to_a.sample
         else
-          (
-            ('Aa'..'Zz').to_a.shuffle.join.chars.sample(sample_size).push(*symbols.shuffle) << rand(0..9)
-          ).shuffle.push(*invalid_symbols.sample(size)).shuffle[0...size].join
+          prepare_user_name(randomizer)
         end
     end
+
+    def randomizer
+      (
+        ('Aa'..'Zz').to_a.shuffle.join.chars.sample(sample_size).push(*symbols.shuffle) << rand(0..9)
+      ).shuffle.push(*invalid_symbols.sample(size)).shuffle[0...size]
+    end
+
+    def prepare_user_name(sample)
+      sample.rotate!(1) while symbols.include?(sample.first)
+      sample.join
+    end
   end
 end
diff --git a/spec/support/helpers/generate_email_helper_spec.rb b/spec/support/helpers/generate_email_helper_spec.rb
index 30e11f6..06ab3fe 100644
--- a/spec/support/helpers/generate_email_helper_spec.rb
+++ b/spec/support/helpers/generate_email_helper_spec.rb
@@ -6,13 +6,17 @@ module Truemail
       context 'without params' do
         subject(:generate_email) { described_class.call }
 
+        let(:allowed_symbols) { %w[@ - _ . +] }
+
         specify { expect(generate_email).to be_an_instance_of(String) }
         specify { 100.times { expect(generate_email.size).to be_between(15, 255) } }
-        specify { 100.times { expect(generate_email).to include(*%w[@ - _ .]) } }
+        specify { 100.times { expect(generate_email[0]).not_to include(*allowed_symbols) } }
+        specify { 100.times { expect(generate_email).to include(*allowed_symbols) } }
       end
 
       context 'with size: :min' do
         specify { expect(described_class.call(size: :min).size).to eq(6) }
+        specify { expect(described_class.call(size: :min)[0]).to match(/[a-z]/) }
       end
 
       context 'with size: :max' do
diff --git a/spec/truemail/configuration_spec.rb b/spec/truemail/configuration_spec.rb
index 1dd672a..9c443d0 100644
--- a/spec/truemail/configuration_spec.rb
+++ b/spec/truemail/configuration_spec.rb
@@ -27,6 +27,14 @@
     let(:default_verifier_domain) { valid_email[/\A(.+)@(.+)\z/, 2] }
 
     context 'when auto configuration' do
+      let(:configuration_instance_expectaions) do
+        expect(configuration_instance.email_pattern).to eq(Truemail::RegexConstant::REGEX_EMAIL_PATTERN)
+        expect(configuration_instance.connection_timeout).to eq(2)
+        expect(configuration_instance.response_timeout).to eq(2)
+        expect(configuration_instance.validation_type_by_domain).to eq({})
+        expect(configuration_instance.smtp_safe_check).to be(false)
+      end
+
       it 'sets configuration instance with default configuration template' do
         expect { configuration_instance.verifier_email = valid_email }
           .to change(configuration_instance, :verifier_email)
@@ -41,11 +49,41 @@
           .and not_change(configuration_instance, :validation_type_by_domain)
           .and not_change(configuration_instance, :smtp_safe_check)
 
-        expect(configuration_instance.email_pattern).to eq(Truemail::RegexConstant::REGEX_EMAIL_PATTERN)
-        expect(configuration_instance.connection_timeout).to eq(2)
-        expect(configuration_instance.response_timeout).to eq(2)
-        expect(configuration_instance.validation_type_by_domain).to eq({})
-        expect(configuration_instance.smtp_safe_check).to be(false)
+        configuration_instance_expectaions
+      end
+
+      it 'sets configuration instance with default configuration template for upcase email' do
+        expect { configuration_instance.verifier_email = valid_email.upcase }
+          .to change(configuration_instance, :verifier_email)
+          .from(nil).to(valid_email)
+          .and change(configuration_instance, :verifier_domain)
+          .from(nil).to(default_verifier_domain)
+          .and change(configuration_instance, :complete?)
+          .from(false).to(true)
+          .and not_change(configuration_instance, :email_pattern)
+          .and not_change(configuration_instance, :connection_timeout)
+          .and not_change(configuration_instance, :response_timeout)
+          .and not_change(configuration_instance, :validation_type_by_domain)
+          .and not_change(configuration_instance, :smtp_safe_check)
+
+        configuration_instance_expectaions
+      end
+
+      it 'sets configuration instance with default configuration template for mixcase email' do
+        expect { configuration_instance.verifier_email = valid_email.capitalize }
+          .to change(configuration_instance, :verifier_email)
+          .from(nil).to(valid_email)
+          .and change(configuration_instance, :verifier_domain)
+          .from(nil).to(default_verifier_domain)
+          .and change(configuration_instance, :complete?)
+          .from(false).to(true)
+          .and not_change(configuration_instance, :email_pattern)
+          .and not_change(configuration_instance, :connection_timeout)
+          .and not_change(configuration_instance, :response_timeout)
+          .and not_change(configuration_instance, :validation_type_by_domain)
+          .and not_change(configuration_instance, :smtp_safe_check)
+
+        configuration_instance_expectaions
       end
     end
 
@@ -78,6 +116,18 @@
               .to change(configuration_instance, :verifier_domain)
               .from(nil).to(valid_domain)
           end
+
+          it 'sets custom verifier domain for upcase domain' do
+            expect { configuration_instance.verifier_domain = valid_domain.upcase }
+              .to change(configuration_instance, :verifier_domain)
+              .from(nil).to(valid_domain)
+          end
+
+          it 'sets custom verifier domain for mixcase domain' do
+            expect { configuration_instance.verifier_domain = valid_domain.capitalize }
+              .to change(configuration_instance, :verifier_domain)
+              .from(nil).to(valid_domain)
+          end
         end
 
         context 'with invalid domain' do
diff --git a/spec/truemail/core_spec.rb b/spec/truemail/core_spec.rb
index 2c1f4b4..21b28b8 100644
--- a/spec/truemail/core_spec.rb
+++ b/spec/truemail/core_spec.rb
@@ -13,6 +13,7 @@ module Truemail
       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) }
     end
 
     describe 'Truemail::RegexConstant::REGEX_EMAIL_PATTERN' do
@@ -38,15 +39,34 @@ module Truemail
         ).to be(false)
       end
 
-      it "allows '-', '_', '.', numbers, letters case insensitive before @domain" do
+      it "allows '-', '_', '.', '+', numbers, letters case insensitive before @domain" do
         expect(regex_pattern.match?(GenerateEmailHelper.call)).to be(true)
       end
 
+      it 'allows tld size between 2 and 63 chars' do
+        expect(regex_pattern.match?('i@i.io')).to be(true)
+        expect(regex_pattern.match?('i@i.io' + 'z' * 61)).to be(true)
+        expect(regex_pattern.match?('i@i.io' + 'z' * 62)).to be(false)
+        expect(regex_pattern.match?('i@i.i')).to be(false)
+      end
+
+      it 'case insensitive' do
+        %w[h@i.io H@i.io h@I.io h@i.Io H@i.Io Ho@iO.Io].each do |email|
+          expect(regex_pattern.match?(email)).to be(true)
+        end
+      end
+
       it 'not allows special chars' do
         expect(
           regex_pattern.match?(GenerateEmailHelper.call(invalid_email_with: %w[! ~ , ' & %]))
         ).to be(false)
       end
+
+      it "not allows '-', '_', '.', '+' for one char username" do
+        expect(
+          regex_pattern.match?(GenerateEmailHelper.call(size: :min, invalid_email_with: %w[- _ . +]))
+        ).to be(false)
+      end
     end
 
     describe 'Truemail::RegexConstant::REGEX_DOMAIN_PATTERN' do
@@ -70,9 +90,11 @@ module Truemail
         expect(regex_pattern.match?('service.subdomain.company.domain')).to be(true)
       end
 
-      it 'allows tld size between 2 and 7 chars' do
+      it 'allows tld size between 2 and 63 chars' do
         expect(regex_pattern.match?('domain.io')).to be(true)
-        expect(regex_pattern.match?('domain.rentals')).to be(true)
+        expect(regex_pattern.match?('domain.iq' + 'z' * 61)).to be(true)
+        expect(regex_pattern.match?('domain.iq' + 'z' * 62)).to be(false)
+        expect(regex_pattern.match?('domain')).to be(false)
       end
 
       it 'not allows dash as last char' do
@@ -83,6 +105,21 @@ module Truemail
       it 'not allows number in tld' do
         expect(regex_pattern.match?('domain.42')).to be(false)
       end
+
+      it 'case insensitive' do
+        %w[domain.io DOMAIN.IO Domain.io DoMain.Io].each do |domain|
+          expect(regex_pattern.match?(domain)).to be(true)
+        end
+      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
   end