You can, in outlook, make a 'form' that prevents the e-mail recipient from
using 'reply' and 'forward' on an e-mail send using that 'form'.

But if there is set a 'rule' to automatic forward the email, then it will be
forwarded regardless what the form says.

Using Outlook as the transmitting and the receiving e-mail program. How do
you defenitly prevent an e-mail to be forwarded - to disgard what ever rules
there may be. In other words; How do you make sure that there is only one
recipient for an email? (of course if the exchange administrator have made
more recipients then its not possible, but if thats not the case).