Klaviyo is the best in class email marketing solution for eCommerce. It's powerful because it connects to your store, and you can create awesome customer segments based on past purchasing behaviors, customer preferences, and even future predictions of spending.

With Mailchimp you can send newsletters and automated emails. You can build your email list with form or import your known contacts. Mailchimp offers pre-designed email templates and a drag and drop email builder.

Omnisend is an omnichannel marketing automation platform for ecommerce businesses. Omnisend allows you to add several channels to the same automation workflow for seamless communication via email, SMS, web push notifications, and more.