Default forward and replay account

Hi,
Is there a setting for default forward and reply email account that
must be always used for sending email? Real situation:
- company with Exchange server 2003 and Outlook 2003
- Most communication uses Exchange server for sending and receiving
emails - it means only one Exchange account in outlook
- one PC must use in Outlook from historical reason together with
Exchange email account alsou POP3 account for downloading emails from
one external account and users resends this emails to other users. This
account should not be used for sending emails. Everything should pass
through the exchange server, it means Exchange account in outlook.

Problem - when user tries to forward email downloaded through the POP3
account in outlook, the email service that will be used to send it is
preset to this POP3 account. User must change manually the account to
the Exchange server. Is it possible to preset that all forwarded (the
same for replied) emails will have set as the default account used for
sending Exchange server? Or is it possible to disable to use for sending
other account than Exchange server?

Thank you for any advice.

regards

Pavel