Question postfix: add custom line in incoming mail

[netc]

hello and excuse my poor English.
hope i'm in the right forum.
i try to find a way to add some custom header to the incoming mail.
so i create /etc/postfix/my_custom_header with this line:
/^X-Original-To: (.*)$/ PREPEND X-Original-dest: $1
but when i reload postfix i have a mail error:
Postfix SMTP server: errors from mail.***.com
....
all i want, is to add a line 'X-Original-dest' in header with the mail adress of X-Original-To cause in all header, i have twice X-Original-To, the first are the right, but the second is with the "To:" address .
i have a account [email protected] without mailbox who forward to user1 and user2 .
user1 and user2 don't have a mailbox, but there's a collector for mails without user account.
so when i send mail to [email protected], i receive two mail in [email protected].
header example:

Return-Path: <[email protected]>
X-Spam-Checker-Version: xxxxx xxxxx
X-Spam-Level: xxxxxxxxxxxx
X-Spam-Status: xxxxxxxxxxxxxxxxxxxxxx
HTML_MESSAGE xxxxxxxxxxx
X-Original-To: [email protected]
Delivered-To: [email protected]
Received: by xxxxxxxxxxxxxxx (Postfix, from userid xxx)

DomainKey-Status: good
X-Original-To: [email protected]
Delivered-To: [email protected]

From: "[NC] me" <[email protected]>
To: <[email protected]>
Subject: test


can someone help me please.