I'm using this just for transactional emails. I have another solution for marketing emails.
I was using SendGrid's WYSIWYG templates for many emails, but I'm re-doing them in my own code so that I can more easily change providers in the future. I'll just need the ability to send HTML emails.
If you are looking for just the visual email template builder part, check out EmailBuilder.js (https://github.com/usewaypoint/email-builder-js) - it's a free and open-source builder that also has a hosted playground.
I was using SendGrid's WYSIWYG templates for many emails, but I'm re-doing them in my own code so that I can more easily change providers in the future. I'll just need the ability to send HTML emails.
I'm trying out MailTrap.