If you do not want your guests on Magento2 store to be able to subscribe to the newsletter or you are facing spam bots registering on store, follow below steps from your store admin to disable the same.
After installing a Magento2 store recently, I started facing issues with spam newsletter subscription and obviously it makes my email service provider unhappy. After searching a lot online, I only got solutions to make code changes. After some research, I found the solution to disable guest newsletter subscription from admin.
Go to Magento2 admin -> Stores -> Customers -> Newsletter ->
Allow Guest Subscription and set the value to NO.
That’s it. Now just clear the cache !!!
Now, go to the storefront and try to subscribe to the newsletter in guest mode. If everything went right, you will see below message:
No need to install any new module, make code changes or install any captcha/recaptcha solutions.
Let me know using the comment form below if you face any issues.