We've seen folks in ecomm generate a lot of revenue using Klaviyo to get in front of their customers and subscribers with segmented newsletters. Klaviyo hooks up with Shopify and other ecomm platforms so you can send emails based on customer behavior and product preferences.
But it's hard to send a lot of emails if what you're sending is only product and discounts - you get subscriber fatigue and more unsubs.
The key is to send valuable content your customers like. Tools like Matcha make it easier to source relevant, ready-to-deploy content to stay in front of your customers without annoying them.