We currently have postfix handling emails generated by a number of apps. A number of these emails are destined for users inside the organisation, whose mail is on an Exchange server in the same site as the postfix box.
I'm looking for a way to do this, but my Google-fu is letting me down:
If the recipient domain is one of our domains, deliver the mail to host mail.example.com. All other mail is delivered by looking up the MX record/s and processing normally.
Edit: to clarify, the apps generating the emails are sending to users outside of our organisation too, postfix is not receiving mail at all.