I think I might not understand this concept, but here goes.
I've set up my postmaster and ExchangeRecipient and NDRs correctly, so that I get a copy of all NDRs to internal recipients.
When an external sender tries to send a message - for example larger than the allowed receive size - I get a proper NDR notification. However, the sender is not getting any bounce notifications. Is that the job of the sender's e-mail server or our Exchange Server ?
As an example, I sent a 15MB attachment to a test internal recipient from my Google Gmail account. Our size limit is 10MB. On the inside, all works perfectly. However, I never receive a notification from Google that my message has bounced. Is that a Google issue or is that a configuration issue on my server ? (Exchange 2010, SP2, RU4).