I don't see any field for which property in this document:
I'm about to update my website to integrate with this.
That is handled by sending the email to the @inquiryspot email address for the property in question.
If you go to the inquiry instructions page seen here:
It shows a specific @inquiryspot email address for each of your properties in OwnerRez.
When the page or form on your website is submitted, have it send the email to the correct @inquiryspot email address and it will land inside OwnerRez properly. Do a couple tests and you'll see if it's working.