Oh wow! I've used them off and on, and haven't really had many issues. Albeit I haven't run into any issues that warranted contacting support, so I have no idea what that's like.
That said, you don't have to use Mailjet the service to use MJML the templating language. I've also used their WYSIWYG editor quite a few times to edit templates and export the HTML and MJML files for use elsewhere.
That said, you don't have to use Mailjet the service to use MJML the templating language. I've also used their WYSIWYG editor quite a few times to edit templates and export the HTML and MJML files for use elsewhere.