Why does MacBook keep re-creating a “Notes” mailbox?

A related question (but not a duplicate) has no answer.

We have a MacBook Pro, two iPads, and an iPhone, all on the same Apple ID. We have four e-mail accounts, but three of them are only on the laptop and one iPad. Every time I look, two or all three of these accounts have sub-mailboxes called Notes. They are always empty, and I immediately delete them.

Several times, I have checked the settings on both devices, and Notes is not checked on any account except iCloud. Nor does either device in the Notes app show any Notes anywhere but iCloud.

Why might these keep appearing and how can I make it stop?

This has been happening for many MacOS and IOS updates. I am currently fully updated and it happened again today.