Disable Newsletter Subscription Success Email. Usually, the people create this email on the marketing side(Klaviyo, Mailchimp), but the option to disable this email is not available by default on Magento/Adobe Commerce
Install using Composer.
composer require pauloharaujos/magento2-disable-newsletter-email
php bin/magento module:enable PHAS_DisableNewsletterEmail
php bin/magento setup:upgrade
Access your Magento Admin Panel, then navigate to Stores -> Settings -> Configuration -> Customers -> Newsletter -> Subscription Options -> Disable Newsletter Confirmation Email Success