[twelvechairs]

I don't know if it's unpopular. That's literally how domains are designed to function and have done by and large for decades

[thanksgiving]

I think marketing folks like to send emails from a different domain so they can send transactional and marketing emails from different domains altogether (not just subdomains). Not sure if this is evidence based or just plain voo doo / monkey-see-monkey-do but I’ve read this in multiple places. But of course, that doesn’t apply here.