Anthony Kamau wrote:

> 3/ if exchange is configured to send a copy of received email to an
> external account OR the message is destined for a non-existent mailbox,
> exchange will initiate a connection with sendmail either for forwarding
> mail or for NDR
> 4/ since the exchange box is now trusted via msa_networks, the email
> receives a clean bill of health from spamassassin and sendmail proceeds
> to remove the headers previously added for the incoming message except
> for the subject line which is left with the previously changed header!
> How can I tell sendmail milter not to remove any of the headers as the
> email message is really still spam???

This depends entirely on the milter. Perhaps you can configure it to
either not scan mail that has already been scanned by your system or to
not scan outgoing mail at all.

In any case, spamming people with backscatter in the form of NDRs from
your system is completely unacceptable. You have at least three options
to prevent this; (i) configure out how to do LDAP queries from Sendmail
against your Exchange system to verify addresses, or (ii) use a milter
such as Anthony Howe's milter-ahead (which I believe he licenses for 90
Euros), or (iii) export all of your addresses to your Sendmail box.