1. Add a column named Status to your hard-bounce file.
2. Populate this field with the word Unsubscribed for each subscriber.
3. Import the hard-bounce file to your All Subscribers list. Upload to your All Subscribers list to avoid future list creation with invalid addresses.
4. Check the Update Subscriber Records checkbox in the Import Wizard.
5. Map the Email Address and Status fields.
6. Import your file.
7. Spot check to ensure that subscribers have been unsubscribed appropriately.