jconfer

I am using WPEngine as a host too. Thanks for sharing what you found out.

I think I figured out the problem. Thank you for your help!

I am also experiencing the same issues. I updated to WP 5.5 and emails have quit sending from the site when our Formidable form is submitted. The test message isn’t sending as well with and without other plugins activated. When we reverted back to 5.4 the plugin works fine.