diff --git a/include/class.format.php b/include/class.format.php
index c6effb45b959d73d2d8b59523e727db2f1742c08..a85d2d69f1f73f3eeee3634118c66be3a1a8bd38 100644
--- a/include/class.format.php
+++ b/include/class.format.php
@@ -426,7 +426,7 @@ class Format {
                 // Scan for things that look like URLs
                 return preg_replace_callback(
                     '`(?<!>)(((f|ht)tp(s?)://|(?<!//)www\.)([-+~%/.\w]+)(?:[-?#+=&;%@.\w]*)?)'
-                   .'|(\b[_\.0-9a-z-]+@([0-9a-z][0-9a-z-]+\.)+[a-z]{2,4})`',
+                   .'|(\b[_\.0-9a-z-]+@([0-9a-z][0-9a-z-]+\.)+[a-z]{2,63})`',
                     function ($match) {
                         if ($match[1]) {
                             while (in_array(substr($match[1], -1),