You must have Admin Level - Superuser access to manage email opt-outs.
To manually unsubscribe a user:
Click Org Tools > Email Center in the left navigation menu.
Click the Manage Opt-Outs tab.
Click + Add Opt-Out.
Enter the email address to unsubscribe.
Click Save.
To delete an email from the opt-out list and re-subscribe it:
Click Org Tools > Email Center in the left navigation menu.
Click the Manage Opt-Outs tab.
Check the box(es) by the desired user(s) name(s) to re-subscribe.
Click Edit > Remove.
Click OK to confirm.
To export unsubscribed users:
Click Org Tools > Email Center in the left navigation menu.
Click the Manage Opt-Outs tab.
Check the box(es) by the desired user(s) name(s) to export.
Click Export > Custom Excel Export.
Select desired fields to include.
Click Create Report.
The file automatically downloads.