Looking for ideas of how to efficiently compare a large external list to the database in order to see if anyone on it is already in the database. Our annual fund team will periodically get a large acquisition list from an external source as part of preparations various appeals. The issue arises when they have to screen that list against our database to make sure that there is no one on it who has opted out of receiving communications from us (which we track in RE). (It also helps to make sure we don't create duplicate records.) This is currently a very manual and time-consuming process and I'm trying to come up with a way to streamline it. Thank you for any ideas or insight you can provide!