Simfatic Forms is being discontinued.
See the announcement →email error: Validation failed
email error: Validation failed for: Some.One<someone@domain.com>
This error is thrown by PHP mail when the email is not in good format
Solution
Enter just the plain email without the name part. For example, in the "form to email" page->recipients list, remove the current emails and add just the email address.
After adding just the email address, re-upload the form.
If you need further help, submit this form.