[Exim] Leaving bcc: headers in mail

Hi

Is there an option to preserve Bcc: headers(including the recipient, not
an empty one) in local mails?

The reason is a setup where mail for a domain is received with exim, then
stored for all users in a single mailbox file, and then retrieved by an
Exchange Server using POP to store it for several Exchange Users. If Bcc:
is removed, Exchange will not deliver it to those users.

P.S. The setup was not my idea...

Bye
Tim