Message scripting HTML and text limitations

In Transact message scripting the default HTML body cannot exceed .5MB (500KB). The default Text body cannot exceed .5MB (500KB). The HTML and Text body sizes are calculated separately.
For Transact message scripting messages when one or both bodies are over the size limit an error will occur.
Saving via the UI: An HTML and/or text body error of size_of_body exceeds the maximum allowed size of .5MB. Reduce the size of the HTML template body and save again.
Saving via API: An HTML and/or text template body error of size_of_body exceeds the maximum allowed size of .5MB. Reduce the size of the HTML template body and save again.
Importing a template: Template cannot exceed .5MB. Reduce the size of the template and import again.

These errors prevent saving. Reduce the size of the template body and save again.
Regarding existing templates that exceed .5MB there is a customized size limit to accommodate them. With existing template sizes that exceed .5MB you can open, modify, and save templates.