As a best practice you should manage your subscription list on a regular basis, and make sure to process any requests to unsubscribe. In some jurisdictions, it is required by law that requests to unsubscribe are processed within a specific period of time.
If you want to use a third-party service to send newsletters, you can export your subscription list as a CSV or XML file.
To cancel a subscription
On the Admin sidebar, tap Marketing. Then under Communications, choose Newsletter Subscribers.
Find the subscriber in the grid. Then, mark the checkbox in the first column.
Set the Action control to “Unsubscribe”. Then, tap Submit.
The status of the record changes to “Unsubscribed”.
To export the list of subscribers
From the Newsletter Subscribers list, use the filter controls to include only records with a Status of “Subscribed,” and for the appropriate website, store, or store view.
Set the Export to control to one of the following:
Tap Export. Then, look for the prompt at the bottom of the screen, and save the file.
Export Newsletter Subscribers