Calc - Keep Only Duplicates


I’m not sure whether I want to keep only duplicates or get rid of duplicates.

I have two CSV’s from MailChimp. They are lists of mailing list subscribers, and many are duplicates between the two as some people signed up for both. One list has first name, last name and “how did you hear about us” as fields. The second has email address only.

I want to keep these as separate lists instead of merging them. That way, the people on list 1 can get personalized emails addressed to their first name. List 2 people will get more generic versions of the same email.

I might need to know how to get a spreadsheet with only email addresses that are on both lists. That way, I can delete them from List 2 in MailChimp individually. Something like this if I’m reading it correctly:

Otherwise, there may be a better idea. Maybe the cleanup can happen all at once, and I’m left with the new version of list 2 in a spreadsheet (the one without anyone who is also on list 1). That would be idea if it’s possible.