With the change from legacy automation to the new automation there doesn't appear to be an email template to send an email. We set these up to ensure consistent formatting of all emails and just enter the content in the automation.
When using the legacy automation the email template set up in Customer notifications is used (this includes content and CSS formatting). However with new automation the send email action doesn't appear to use this template.
Instead the emails seem to get some mime formatting surrounding the email content and html tags (eg <br />) included in the email. I have set the emails to send as HTML and enabled convert line breaks to HTML line breaks.
Please add usage of email templates to the send email action