Earlier quoted context omitted.
Why does any company needs more than one 2nd level domain? Microsoft, I'm looking at you ( https://learn.microsoft.com/en-us/microsoft-365/enterprise/u... ). It nerve-wrecking trying to figure out if some login box or link is legit. They claim to be transitioning to cloud.microsoft, but if you go there, you are redirected to yet another new domain (microsoft365.com) which looks like a scam site, which doesn't render…
Domains used for bulk outbound email are typically separated from the normal corporate email domain to prevent employee emails getting blocked at customer mail gateways by anti-spam heuristics. Practically every large org gets burnt by this once, learns their lesson, and then splits their domains. Microsoft has something like a hundred domains, including purposefully misspelled ones like "microsft.com", which is real…
You are off by orders of magnitude there on that number.