Your audience list is yours. Export it any time.
Where
Dashboard, Audience section, Export. We send a CSV with the confirmed addresses and the date each one signed up.
What is not in the export
Unconfirmed addresses and people who unsubscribed. We keep those records internally to honor opt outs, we do not hand them out.
If you delete your account
Your audience list is deleted with you. Export first if you want to keep it.