ConvertKit is an email marketing automation platform aimed at professional bloggers, course creators, and online business owners. It allows users to create and segment email lists, design custom email templates, and automate email sequences, all while providing robust analytics and integrations with other tools.
Sendinblue is a cloud-based marketing automation and email marketing platform that provides tools to manage contact lists, create email templates, automate email campaigns, and analyze engagement metrics. It offers an API that allows developers to integrate the platform with external applications and web services.