Postfix - Prevent multiple RCPT from exchange server

Question

For a particular requirement to just collect incoming emails, I use milter to write and not queue further. Though the same postfix handles two domains, however I need to allow only one RCPT per email (it can have multiple To: not an issue). Found that ms-exchange (sender) at times combines multiple RCPTs in the same email submission to postfix, when it had to send two same emails to both the domains this postfix supports.
What is this functionality of combining RCPTs called, any idea how to prevent this from happening in sender's (exchange) side or receiver (postfix)

Answer 1

Here's a similar thread and it explains that Assuming the e-mail client sends the message only once, and the receiving domain allows multiple RCPT TO addresses for a message, then there's only one e-mail to the other domain and there well be three "RCPT TO" addresses. Another detailed information you could refer to the similar thread.