Index: /trunk/roundcubemail/CHANGELOG
===================================================================
--- /trunk/roundcubemail/CHANGELOG	(revision 5968)
+++ /trunk/roundcubemail/CHANGELOG	(revision 5969)
@@ -2,4 +2,5 @@
 ===========================
 
+- Fix handling of % character in IMAP protocol (#1488382)
 - Fix duplicate names handling in addressbook searches (#1488375)
 - Fix displaying HTML messages from Disqus (#1488372)
Index: /trunk/roundcubemail/program/include/rcube_imap_generic.php
===================================================================
--- /trunk/roundcubemail/program/include/rcube_imap_generic.php	(revision 5968)
+++ /trunk/roundcubemail/program/include/rcube_imap_generic.php	(revision 5969)
@@ -3617,11 +3617,14 @@
             return 'NIL';
         }
+
         if ($string === '') {
             return '""';
         }
+
         // atom-string (only safe characters)
-        if (!$force_quotes && !preg_match('/[\x00-\x20\x22\x28-\x2A\x5B-\x5D\x7B\x7D\x80-\xFF]/', $string)) {
+        if (!$force_quotes && !preg_match('/[\x00-\x20\x22\x25\x28-\x2A\x5B-\x5D\x7B\x7D\x80-\xFF]/', $string)) {
             return $string;
         }
+
         // quoted-string
         if (!preg_match('/[\r\n\x00\x80-\xFF]/', $string)) {