I love using MJML to craft email newsletters, I've been using it for a few years now and it's a great way to create emails.
MJML stands for "Mailjet Markup Language". MJML has been designed to reduce the pain of coding a responsive email. Leveraging its semantic syntax and a rich standard components library, making your email responsive is not an issue anymore.
To learn more about MJML check out their site
I've created an MJML editor in Audience, this allows you to use MJML to create the email and then see a preview of what it will look like as an email.
Once you are happy with the email, you can select "Generate Email" and this will open the normal email editor with your new email already loaded.
You can make any finishing touches you want to here.
Our editor has a built-in preview tool, so at any stage you can send yourself a preview of the email to see how it will look
Save As Draft
It does what it says on the button, saves the newsletter as a draft so you can come back to it at any time.
Schedule the email when you are ready. Set it to send when you want.