Index: wp-includes/formatting.php
===================================================================
--- wp-includes/formatting.php	(revision 14235)
+++ wp-includes/formatting.php	(working copy)
@@ -1520,12 +1520,6 @@
 		}
 	}
 
-	// DNS
-	// Check the domain has a valid MX and A resource record
-	if ( $check_dns && function_exists( 'checkdnsrr' ) && !( checkdnsrr( $domain . '.', 'MX' ) || checkdnsrr( $domain . '.', 'A' ) ) ) {
-		return apply_filters( 'is_email', false, $email, 'dns_no_rr' );
-	}
-
 	// Congratulations your email made it!
 	return apply_filters( 'is_email', $email, $email, null );
 }