> If a user sends a mail and postfix can?t deliver it (user unknown,
> mailbox quota, etc.), this user gets the error message.
> Is it possible to configure postfix in such a way, that these error
> messages are going to a different mailbox?
The SMTP standard requires that errors are reported to the MAIL
FROM address (it's not just Postfix, but every other mail server
that plays by the rules). If you prefer to receive errors in a
particular place, configure the sending program accordingly.