Server mail setup specialist required

We have two servers based in San Francisco that send outbound only SMTP emails to candidates (and then process the responses). We use a Hosted Exchange service (nothing to do with the servers) which has the email account attached to it that the server mails appear to be sent from (admin@...). What we want to do is to set up the outbound SMTP service on the servers and our Hosted Exchange service in such a way that we get delivery and relay receipts sent to the Hosted Exchange service, not returned to the server, even though the messages originate from the server. We also need to do this without enabling mail relay on the server as we were spammed to a standstill last time we tried that. Please ask if you have any further questions.