Cannot disable iCloud email forward

I am having the same problem as that raised by zturn99 on 27th May 2022.

I recently retired from teaching and to make it easier for me to keep track of my incoming personal icloud emails while I was employed at the institution I had them forwarded to my workplace outlook address. Since retirement I have been able to change this feature in my icloud settings but my emails are still being forwarded. To make things worse, my previous employer has removed my email account from their system and so every time I receive an email in icloud (which is then forwarded to my previous employer) I receive a postmaster response from Office 365 saying that the email is undeliverable, and this feeds into my inbox and is then also forwarded!

Why are my incoming emails still being forwarded even though I have disabled the feature in settings, and how can I stop this happening?

Thanks

FYI - I have two devices, an imac and a macbook pro and I have checked that the forwarding feature is disabled on both and that their are no other rules that might cause this. I also receive icloud emails on my iphone, but I am not aware that this has an automatic forwarding feature.