This would be a function of GIM using the above method or the LDAP group (which is actually a container, not group lookup).
For XMC, you can specify predefined addresses - not wildcards, any sponsor or a specific sponsor (not exposed to the end user). Wildcard domains are not an option in XMC, although I’m not sure you’d want the CEO receiving sponsorship requests .
That said, you could use a similar group option as GIM, but put your sponsors into a specific email group and use that as your sponsor email.bEvery sponsor would be notified, but at least it wouldn’t be upper management or some guy in accounting wondering why he’s getting sponsor requests.