In the Subscription Center, export entire specific mailing lists or just the Opted-Ins or Opted-Outs from a specific list.
Export Mailing Lists
Select the Profile tab.
On the Subscriptions tab, select Subscription Center, then Download.
Choose an Export option for the list you wish to download: All Email Addresses, Opted-In or Opted-Out.
Browse to your Download folder to locate the exported list.