Apple Mail - ...@icloud.com email address

I have seen this question before - at least I think I've seen it before (the answers are never relevant to what I think the question is, though!) To put it in the most simple language I can:

I have a mac.

)n that mac is an application - and email client called "Mail".

I have set up an email address in "Mail" that I use regularly (it's actually my business email).

I may have also set up the an .....@icloud.com address (but I don't think I did).

I see no point in this ...@icloud.com email address - it is not used (and if it was I'd use another email client or access it through "iCloud" itself - "Mail" is for my business emails).

I would like to remove the @icloud.com email address from "Mail". but when I try to do so I am warned that "this iCloud ID (which is my personal email address) is used in other applications" ..... to be clear, my icloud.com email address is NOT my iCloud ID.... and that I can remove it is "Internet accounts".... but there's no option there....