No body specified

I searched for other posts with the same error message but didn’t find an answer to my specific situation. I’m getting the following error message when Formidable Forms Pro sends an email via Post SMTP:

You getting this message because an error detected while delivered your email.
For the domain: (my website’s domain)
The log to paste when you open a support issue:
No body specified

`
All of the emails are complete and have content in the body of the emails. Is there a way I can suppress the false notifications?