You can use our built-in newsletter widget to signup guests without a third party integration. This may already be installed on your store home page or you can add it using the widgets by going to Appearance → Layouts in the admin.
⚠️ Pro Tip: third party newsletter/email list services are great. To see how to integrate those just click to search newsletter in our docs.
Export Your Subscriber List
To export a CSV of your list of subscribers simply open Reports → Customer → Guest Newsletter Signups in the admin.