Can Salesforce de-duplicate leads before they are sent to me?

A majority of the partners we polled requested that we send them all the leads. We designate duplicate AppExchange leads as follows: SFDC-dup-XX|Listing Name.

If the source code contains -dup-, then AppExchange already sent you a lead for this user, listing, or action within the last 180 days. For example, SFDC-dup-DM|VerticalResponse for AppExchange indicates a duplicate lead from a user who clicked to view the demo video on the VerticalResponse for AppExchange listing.