diff --git a/class.phpmailer.php b/class.phpmailer.php
index 1c157474..c49bb7d1 100644
--- a/class.phpmailer.php
+++ b/class.phpmailer.php
@@ -447,6 +447,15 @@ class PHPMailer
      */
     public $XMailer = '';
 
+    /**
+     * Which validator to use by default when validating email addresses.
+     * May be a callable to inject your own validator, but there are several built-in validators.
+     * @see PHPMailer::validateAddress()
+     * @var string|callable
+     * @static
+     */
+    public static $validator = 'auto';
+
     /**
      * An instance of the SMTP sender class.
      * @var SMTP
@@ -1028,19 +1037,30 @@ class PHPMailer
     /**
      * Check that a string looks like an email address.
      * @param string $address The email address to check
-     * @param string $patternselect A selector for the validation pattern to use :
+     * @param string|callable $patternselect A selector for the validation pattern to use :
      * * `auto` Pick best pattern automatically;
      * * `pcre8` Use the squiloople.com pattern, requires PCRE > 8.0, PHP >= 5.3.2, 5.2.14;
      * * `pcre` Use old PCRE implementation;
      * * `php` Use PHP built-in FILTER_VALIDATE_EMAIL;
      * * `html5` Use the pattern given by the HTML5 spec for 'email' type form input elements.
      * * `noregex` Don't use a regex: super fast, really dumb.
+     * Alternatively you may pass in a callable to inject your own validator, for example:
+     * PHPMailer::validateAddress('user@example.com', function($address) {
+     *     return (strpos($address, '@') !== false);
+     * });
+     * You can also set the PHPMailer::$validator static to a callable, allowing built-in methods to use your validator.
      * @return boolean
      * @static
      * @access public
      */
-    public static function validateAddress($address, $patternselect = 'auto')
+    public static function validateAddress($address, $patternselect = null)
     {
+        if (is_null($patternselect)) {
+            $patternselect = self::$validator;
+        }
+        if (is_callable($patternselect)) {
+            return call_user_func($patternselect, $address);
+        }
         //Reject line breaks in addresses; it's valid RFC5322, but not RFC5321
         if (strpos($address, "\n") !== false or strpos($address, "\r") !== false) {
             return false;
diff --git a/test/phpmailerTest.php b/test/phpmailerTest.php
index e41a0d61..69eba1e7 100644
--- a/test/phpmailerTest.php
+++ b/test/phpmailerTest.php
@@ -515,7 +515,7 @@ class PHPMailerTest extends PHPUnit_Framework_TestCase
             '"Doug "Ace" L."@iana.org',
             'Doug\ \"Ace\"\ L\.@iana.org',
             'hello world@iana.org',
-            //'helloworld@iana .org',
+            'helloworld@iana .org',
             'gatsby@f.sc.ot.t.f.i.tzg.era.l.d.',
             'test.iana.org',
             'test.@iana.org',
@@ -606,7 +606,9 @@ class PHPMailerTest extends PHPUnit_Framework_TestCase
             'first.last@[IPv6:a1:a2:a3:a4:b1:b2:b3:]',
             'first.last@[IPv6::a2:a3:a4:b1:b2:b3:b4]',
             'first.last@[IPv6:a1:a2:a3:a4::b1:b2:b3:b4]',
-            "(\r\n RCPT TO:user@example.com\r\n DATA \\\nSubject: spam10\\\n\r\n Hello,\r\n this is a spam mail.\\\n.\r\n QUIT\r\n ) a@example.net" //This is valid RCC5322, but we don't want to allow it
+            //This is a valid RCC5322 address, but we don't want to allow it for obvious reasons!
+            "(\r\n RCPT TO:user@example.com\r\n DATA \\\nSubject: spam10\\\n\r\n Hello,\r\n".
+                " this is a spam mail.\\\n.\r\n QUIT\r\n ) a@example.net"
         );
         // IDNs in Unicode and ASCII forms.
         $unicodeaddresses = array(
@@ -657,6 +659,53 @@ class PHPMailerTest extends PHPUnit_Framework_TestCase
         $this->assertFalse(PHPMailer::validateAddress('bad', 'noregex'));
     }
 
+    /**
+     * Test injecting a custom validator.
+     */
+    public function testCustomValidator()
+    {
+        //Inject a one-off custom validator
+        $this->assertTrue(
+            PHPMailer::validateAddress(
+                'user@example.com',
+                function ($address) {
+                    return (strpos($address, '@') !== false);
+                }
+            ),
+            'Custom validator false negative'
+        );
+        $this->assertFalse(
+            PHPMailer::validateAddress(
+                'userexample.com',
+                function ($address) {
+                    return (strpos($address, '@') !== false);
+                }
+            ),
+            'Custom validator false positive'
+        );
+        //Set the default validator to an injected function
+        PHPMailer::$validator = function ($address) {
+            return ('user@example.com' === $address);
+        };
+        $this->assertTrue(
+            $this->Mail->addAddress('user@example.com'),
+            'Custom default validator false negative'
+        );
+        $this->assertFalse(
+            //Need to pick a failing value which would pass all other validators
+            //to be sure we're using our custom one
+            $this->Mail->addAddress('bananas@example.com'),
+            'Custom default validator false positive'
+        );
+        //Set default validator to PHP built-in
+        PHPMailer::$validator = 'php';
+        $this->assertFalse(
+            //This is a valid address that FILTER_VALIDATE_EMAIL thinks is invalid
+            $this->Mail->addAddress('first.last@example.123'),
+            'PHP validator not behaving as expected'
+        );
+    }
+
     /**
      * Word-wrap an ASCII message.
      */