I'm not using the recipients table and I'm sending to a list of email addresses contained in an external data file. I need to do a split and deduplication. How do I do these actions on an external file?

Is it possible to send the same version of an email as only 1 copy of the file (not duplicates) to split target groups each with a wait - I guess basically a Drip Campaign? We've only been able to make it work with using multiple copies of the same email, and this is not exactly optimal. What we are doing is targeting based on the last time a customer opened an email from us, then we separate them out into different groups and send to each group with a wait - ie, send to 30 day openers immediate...