JSM Customer permission question for email submissions

[Karin Stevenson]

I have two spaces in JSM that should have very different permissions:

1. Space is use to collect document approval requests from anyone. There are so many different entities that can send them that I cannot restrict by domain. These folks will only submit by email and not have access to the actual portal, at least not in the beginning.

2. Space is the internal helpdesk that should only allow email submissions from people with specific domains. These customers should have access to email submissions and portal access to submit tickets.

I can see that I can restrict by domain in the Customer Access screen in the /jira/settings/products/servicedesk/customer-access but that seems to control all JSM spaces, so I cannot lock that down by domain because it will restrict the first space.

On the Project settings for Customer access, I can only set Open or Restricted. Restricted is not feasible because anyone with a specific domain should be able to submit email requests and access the Portal but no one that doesn't have one of these emails should be able to. 

How can I keep one Space wide open to allow anyone to send email submissions but lock down the second space down to specific domains only?

I'd be really grateful for some help. It seems like the documentation is somewhat stuck between the old and the new navigation and is not clear.

Thank you!