I know a few. Heck, I’ve worked at such a place, we strictly checked MX records to make sure the email would be reachable, and catch-alls usually wouldn’t pass

I know a few. Heck, I’ve worked at such a place, we strictly checked MX records to make sure the email would be reachable, and catch-alls usually wouldn’t pass validation. (I’m not saying we should have been doing that, but the company was in insurance and wanted to be extra extra sure.)