"From" field is not set for recipient_emails_format.
I get this error when using an email address in the recipient email to field of the custom form email screen.
the form works when I use the asset selector below to select a user but not when I just type in an email address I want the form contents to be sent to!
If you provide an email address, you need to click the "Add" button next to the address so that its saved properly. Its a little counter-intuitive, I know.