I've been using MailChimp for marketing emails but send Grid for automating welcome and password reset emails. Send grid is kinda limited on its builder though.
I use them for my product, www.emailemu.com, which is a tool to help email markers discover email from other companies.
I'm currently using ConvertKit for my email marketing, and I completely agree with you about its simplicity and effectiveness. ConvertKit has proven to be a valuable tool for managing my email campaigns with its user-friendly interface and powerful automation features. The simplicity of ConvertKit makes it easy to create and send targeted emails, and the platform's focus on helping creators and small businesses is evident in its functionality. While I haven't extensively tried other platforms, ConvertKit has met my needs exceptionally well. So if you need complete guide about ConvertKit visit Insight Corridor.
Kastro