Upfront Contact form not arriving anywhere

Hi There

I am using the default Contact page within the Spirit theme. There is a blank field under the General Settings (using Upfront) that says "Send form content to:". I presume that if this is blank then it uses the default site email address but if we put a specific address one in, the form details are then forwarded on to that address instead.

We have tried this both ways and never get the email. Even though there is a confirmation displayed say that the email was sent successfully.

There must be something simple going on here. Can you please advise.