Microsoft's email management has some neat perks here: You can change which one's the primary as well. It's entirely possible for you to change the email address of your Microsoft account, by adding an alias, making it primary, and then deleting the original. In fairness, there are some quirks with this, my old email address would still get sent some receipts or some newsletters because the configuration for service A, B, or C was buried somewhere else in the account. But generally speaking, it works pretty well.

As someone who changed their name but had to keep their Google account with the old one because of how much Google account data/purchases can't be moved to a new account, this felt positively revolutionary. Google accounts can only have one Gmail address for their entire lifetime.