CI_Email::valid_email() hostname validation

valid_email.patch

diff --git a/system/libraries/Email.php b/system/libraries/Email.php
index c70144f..8968a84 100644
--- a/system/libraries/Email.php
+++ b/system/libraries/Email.php
@@ -704,11 +704,37 @@ class CI_Email {
 	 * Email Validation
 	 *
 	 * @param	string
+	 * @param	mixed	types of records to check
 	 * @return	bool
 	 */
-	public function valid_email($address)
+	public function valid_email($address, $options = FALSE)
 	{
-		return (bool) preg_match('/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@([a-z0-9\-]+\.)+[a-z]{2,6}$/ix', $address);
+		if ( ! preg_match('/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@([a-z0-9\-]+\.)+[a-z]{2,6}$/ix', $address))
+		{
+			return FALSE;
+		}
+		elseif (empty($options) OR ! function_exists('checkdnsrr')) // Doesn't exist under Windows prior to PHP 5.3
+		{
+			return TRUE;
+		}
+
+		$options = strtoupper($options);
+		sscanf($address, '%s@%s', &$name, &$host);
+
+		if ($options === 'MX' && ! checkdnsrr($host, $options))
+		{
+			return FALSE;
+		}
+		elseif (CI_Input::valid_ip($host))
+		{
+			return TRUE;
+		}
+		elseif (in_array($options, array('A', 'AAAA'), TRUE))
+		{
+			return checkdnsrr($address, 'A') OR checkdnsrr($address, 'AAAA');
+		}
+
+		return checkdnsrr($address);
 	}
 
 	// --------------------------------------------------------------------