diff --git a/src/Gordianus.php b/src/Gordianus.php
index 29a43b1..5d6807b 100644
--- a/src/Gordianus.php
+++ b/src/Gordianus.php
@@ -24,9 +24,12 @@ class Gordianus
 
     private $services;
 
-    public function __construct(array $services = self::ALL_SERVICES)
+    private $caseSensitiveLocalPart;
+
+    public function __construct(array $services = self::ALL_SERVICES, bool $caseSensitiveLocalPart = false)
     {
         $this->services = $services;
+        $this->caseSensitiveLocalPart = $caseSensitiveLocalPart;
     }
 
     /**
@@ -37,8 +40,10 @@ class Gordianus
     public function getPrimaryEmail(string $email)
     {
         $this->validateEmailAddress($email);
-        $email = strtolower($email);
-        list(, $domain) = explode('@', $email);
+        if (!$this->caseSensitiveLocalPart) {
+            $email = strtolower($email);
+        }
+        $domain = strtolower(explode('@', $email)[1]);
         $result = $email;
 
         foreach ($this->services as $serviceClass) {
diff --git a/src/Services/GmailCOM.php b/src/Services/GmailCOM.php
index a1c496f..a933ea1 100644
--- a/src/Services/GmailCOM.php
+++ b/src/Services/GmailCOM.php
@@ -9,13 +9,13 @@ class GmailCOM implements ServiceInterface
 {
     public function getPrimaryEmail(string $email) : string
     {
-        list($name, $domain) = explode('@', $email);
+        list($name, $domain) = explode('@', strtolower($email));
 
         return explode('+', str_replace('.', '', $name))[0] . '@' . $domain;
     }
 
     public function isDomainSupported(string $domain) : bool
     {
-        return $domain === 'gmail.com';
+        return strtolower($domain) === 'gmail.com';
     }
 }
\ No newline at end of file
diff --git a/src/Services/MultiDomain.php b/src/Services/MultiDomain.php
index 4ac1233..3f71076 100644
--- a/src/Services/MultiDomain.php
+++ b/src/Services/MultiDomain.php
@@ -9,12 +9,20 @@ abstract class MultiDomain implements ServiceInterface
 {
     public function getPrimaryEmail(string $email) : string
     {
+        if (!$this->isCaseSensitive()) {
+            $email = strtolower($email);
+        }
         return explode('@', $email)[0] . '@' . $this->getPrimaryDomain();
     }
 
     public function isDomainSupported(string $domain) : bool
     {
-        return in_array($domain, $this->getDomainList());
+        return in_array(strtolower($domain), $this->getDomainList());
+    }
+
+    protected function isCaseSensitive() : bool
+    {
+        return false;
     }
 
     abstract protected function getPrimaryDomain() : string;
diff --git a/src/Services/WWW33MailCOM.php b/src/Services/WWW33MailCOM.php
index 32b9110..fa40b72 100644
--- a/src/Services/WWW33MailCOM.php
+++ b/src/Services/WWW33MailCOM.php
@@ -9,13 +9,13 @@ class WWW33MailCOM implements ServiceInterface
 {
     public function getPrimaryEmail(string $email) : string
     {
-        list(, $domain) = explode('@', $email);
+        list(, $domain) = explode('@', strtolower($email));
 
         return preg_replace('/\\.33mail\\.com$/', '', $domain) . '@' . $domain;
     }
 
     public function isDomainSupported(string $domain) : bool
     {
-        return (bool) preg_match('/\\.33mail\\.com$/', $domain);
+        return (bool) preg_match('/\\.33mail\\.com$/', strtolower($domain));
     }
 }
\ No newline at end of file
diff --git a/tests/GordianusTest.php b/tests/GordianusTest.php
index f4fd7e8..1fb79a8 100644
--- a/tests/GordianusTest.php
+++ b/tests/GordianusTest.php
@@ -46,6 +46,8 @@ class GordianusTest extends \PHPUnit_Framework_TestCase
         return [
             [new Gordianus([Gordianus::SERVICE_TLEN_PL]), 'john.doe+alias@gmail.com', 'john.doe+alias@gmail.com'],
             [new Gordianus(), 'john.doe+alias@gmail.com', 'johndoe@gmail.com'],
+            [new Gordianus([]), 'John.Doe@example.com', 'john.doe@example.com'],
+            [new Gordianus([], true), 'John.Doe@example.com', 'John.Doe@example.com'],
         ];
     }
 }
\ No newline at end of file
diff --git a/tests/Services/GmailCOMTest.php b/tests/Services/GmailCOMTest.php
index f220938..36ea4bf 100644
--- a/tests/Services/GmailCOMTest.php
+++ b/tests/Services/GmailCOMTest.php
@@ -21,6 +21,7 @@ class GmailCOMTest extends \PHPUnit_Framework_TestCase
     {
         return [
             ['foo.bar@gmail.com', 'foobar@gmail.com'],
+            ['Foo.Bar@GMAIL.COM', 'foobar@gmail.com'],
             ['foobar+alias@gmail.com', 'foobar@gmail.com'],
             ['fo.ob.ar+alias@gmail.com', 'foobar@gmail.com'],
         ];
@@ -41,6 +42,7 @@ class GmailCOMTest extends \PHPUnit_Framework_TestCase
     {
         return [
             ['gmail.com', true],
+            ['gmail.COM', true],
             ['google.com', false],
             ['gmailcom', false],
             ['g.mail.com', false]
diff --git a/tests/Services/WWW33MailCOMTest.php b/tests/Services/WWW33MailCOMTest.php
index 4fe82d9..cbda8ab 100644
--- a/tests/Services/WWW33MailCOMTest.php
+++ b/tests/Services/WWW33MailCOMTest.php
@@ -22,6 +22,7 @@ class WWW33MailCOMTest extends \PHPUnit_Framework_TestCase
         return [
             ['foo.33mail.com', true],
             ['bar.33mail.com', true],
+            ['bar.33Mail.Com', true],
             ['foo.34mail.com', false],
             ['foo33mail.com', false],
         ];
@@ -43,6 +44,7 @@ class WWW33MailCOMTest extends \PHPUnit_Framework_TestCase
         return [
             ['qwerty@name.33mail.com', 'name@name.33mail.com'],
             ['lorem@ipsum.33mail.com', 'ipsum@ipsum.33mail.com'],
+            ['lorem@Ipsum.33mail.com', 'ipsum@ipsum.33mail.com'],
         ];
     }
 }
\ No newline at end of file