do not report attachments sent to some users

[Nerijus Baliunas]

Hello,

I have a mail backup configured in postfix, so that all received and sent messages are forwarded to
backup-recvd-username at example.com and backup-sent-username at example.com.
The problem is when disallowed attchment is sent.
Sending user gets:

Our e-mail content detector has just been triggered by a message you sent:

  To: backup-sent-user at example.com, email at example2.com
or:
  To: backup-recvd-user at example.com, user at example.com
  Subject: ...
  Date: Fri Feb 19 09:45:41 2021

One or more of the attachments (2021 02 18.doc) are on the list of unacceptable attachments for this site and will not have been delivered.

How do I hide these backup-recvd-user at example.com and backup-sent-user at example.com?
I tried adding:
Allow Filenames = %rules-dir%/filename_allow.rules

filename_allow.rules:

To:    backup-recvd-*@example.com       \.*$
To:    backup-sent-*@example.com        \.*$

FromOrTo:       default

But then message with disallowed attachment is delivered to both backup-recvd-user at example.com and user at example.com.

Regards,
Nerijus