If you have blog subscribers via Feedburner and want to start using MailChimp, you can import them easily.
– Log into your Feedburner account.
– Select your feed.
– Go to PUBLICIZE > EMAIL SUBSCRIPTIONS > SUBSCRIPTION MANAGMENT.
– At the bottom of the page, you can see how many subscribers do you have, click on VIEW SUBSCRIBERS DETAILS > EXPORT: CSV > Download the file.
– In MailChimp, go to LISTS > Enter to the list where you want to add the new subscribers > ADD SUBSCRIBERS > IMPORT SUBSCRIBERS.
– Select the CSV option > NEXT > Upload the file you downloaded from Feedburner.