Hey! I am one of Mail Studio's authors. Will be happy to answer any questions.
> Email Previews
> Quickly preview your design on real devices or share it with your team by sending it as an email message.
But when I read the documentation, it seems like you just assume the user has a Litmus account. Is that correct?
Given your paid plans start at $19.99/mo, I think it would be wise to be upfront about the fact that you need a $99/mo Litmus account for this feature to work. Mail client compatibility is the most complex and difficult thing to get right with HTML email design. If you need an external service to get this right, this needs to be clearer. Right now it seems you’re selling Litmus as if it’s your own functionality then expecting your customers to then go and pay much more to Litmus to actually get that functionality.