This is not currently feasible. Recovery Manager for Exchange (RME) AM edition can check for duplicates in the target storage. In the case where the target is an empty PST file checking for duplicates is not of any use.
RME cannot check if the email has already been reconstructed in the Exchange mailbox and based on this decide whether to export the message in the PST file.
If, on the other hand, the target was the exchange mailbox itself (i.e. exporting from AM mailbox straight into Exchange mailbox) then the check for duplicates would make sense.
