You should be able to use a combination of SMTP Send Adapter and POP3 Receive adapter to send emails and retrieve responses.
You will need to add a mailbox for responses and set the From address on the Biztalk send port to this mailbox. You will need POP3 functionality on the exchange server and have a POP3 adapter polling this mailbox.
Your biggest difficulty is going to be determining if an email has been delivered. In the age of spam most people have disabled external delivery receipts and read receipts. You will possibly get bounce messages so you will have to deal with acks and nacks.
The response messages are meant for human consumption so they will not be structured data so parsing the responses will be a nightmare. As will correllating the responses to the originating messages.
Best of luck.