diff --git a/phpBB/develop/calc_email_hash.php b/phpBB/develop/calc_email_hash.php
new file mode 100644
index 0000000000..a67b0f52a3
--- /dev/null
+++ b/phpBB/develop/calc_email_hash.php
@@ -0,0 +1,76 @@
+<?php
+// -------------------------------------------------------------
+//
+// $Id$
+//
+// FILENAME  : calc_email_hash.php
+// STARTED   : Tue Feb 03, 2004
+// COPYRIGHT : © 2004 phpBB Group
+// WWW       : http://www.phpbb.com/
+// LICENCE   : GPL vs2.0 [ see /docs/COPYING ] 
+// 
+// -------------------------------------------------------------
+
+//
+// Security message:
+//
+// This script is potentially dangerous.
+// Remove or comment the next line (die(".... ) to enable this script.
+// Do NOT FORGET to either remove this script or disable it after you have used it.
+//
+die("Please read the first lines of this script for instructions on how to enable it");
+@set_time_limit(300);
+
+$db = $dbhost = $dbuser = $dbpasswd = $dbport = $dbname = '';
+
+define('IN_PHPBB', 1);
+define('ANONYMOUS', 1);
+$phpEx = substr(strrchr(__FILE__, '.'), 1);
+$phpbb_root_path='./../';
+include($phpbb_root_path . 'config.'.$phpEx);
+require($phpbb_root_path . 'includes/acm/acm_' . $acm_type . '.'.$phpEx);
+require($phpbb_root_path . 'includes/db/' . $dbms . '.'.$phpEx);
+include($phpbb_root_path . 'includes/functions.'.$phpEx);
+
+$cache		= new acm();
+$db			= new sql_db();
+
+// Connect to DB
+$db->sql_connect($dbhost, $dbuser, $dbpasswd, $dbname, $dbport, false);
+
+$start = 0;
+do
+{
+	// Batch query for group members, call group_user_del
+	$sql = "SELECT user_id, user_email 
+		FROM  {$table_prefix}users
+		LIMIT $start, 100";
+	$result = $db->sql_query($sql);
+
+	if ($row = $db->sql_fetchrow($result))
+	{
+		do
+		{
+			$sql = "UPDATE {$table_prefix}users 
+				SET user_email_hash = " . (crc32(strtolower($row['user_email'])) . strlen($row['user_email'])) . '
+				WHERE user_id = ' . $row['user_id'];
+			$db->sql_query($sql);
+
+			$start++;
+		}
+		while ($row = $db->sql_fetchrow($result));
+
+		echo "<br />Batch -> $start\n";
+		flush();
+	}
+	else
+	{
+		$start = 0;
+	}
+	$db->sql_freeresult($result);
+}
+while ($start);
+
+echo "<p><b>Done</b></p>\n";
+ 
+?>
\ No newline at end of file