The problem with Enfold and SMTP server is that contact form sender is an account that doesn’t exist in SMTP server.
Supose yo send an email, and you fill your email address in contact form like (Email address hidden if logged out) , but smtp server is smtp.bbb.com.
aaa.com and bbb.com doesn’t match so email won’t send.
I have modified class-form-generator.php file setting a valid sender email address and it works. Simple.
It would be a GREAT idea to be able to select sender when building contact form.
;)