Managing Mailinglists from fans

I have several email contacts of clients, that I've been collecting from these last years.
I can contact from several different lists and servers, but I would like to merge them all as one list, checking for duplicate e-mail entries and keeping the first and last name.

I can do all this manually, but it will take me a lot of work.
Is there a free automated option for this?
Any program, or addon or extra?

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