Use in_array instead of strpos

inc/email_functions.inc.php

@@ -343,8 +343,9 @@ function mfh_sendOverdueTicketReminder($ticket, $users, $modsForHesk_settings) {
         $emails[] = $ticket['user_email'];
     }
     foreach ($users as $user) {
+        $categories = explode(',', $user['categories'])
         if ($user['email'] != $ticket['user_email']
-            && ($user['isadmin'] || strpos($user['categories'], $ticket['category']) !== false)) {
+            && ($user['isadmin'] || in_array($ticket['category'], $categories))) {
             $emails[] = $user['email'];
         }
     }