Hi,

Our automatic de-dupe feature should prevent two of the same record from being uploaded twice the vast majority of the time – especially from the same list source. So this should not be a difficult issue. After you upload the new list of 15000, simply do an advanced search for voters who have never been contacted, save them to a list, and then set your next email blast to that list.

Let me know if this resolves the issue.

ahem continuing the question: So, first of all, it’s a bit tricky trying to get the whole CSV of recipients into the list. Second, I have the following problem: I sent an e-mail blast to the first 5,000 that made it into the NationBuilder list. I want to re-import the CSV to get the other 15000 emails in the list, and then send the first email to the new members of the list. I can tag the 5000, if that would help – but does NationBuilder automatically prevent the same email from being sent to those 5000 addresses? E.g. could I send that same blast, using the same list (after it has been updated) and have NationBuilder automatically not repeat the email to the first 5000 recipients? Or will I have to manage that manually, by tagging the existing 5000?
Also, is there a better way to import long file lists like the one I used? The importing takes a long time and didn’t complete.