Apple Mail App not syncing between iDevices

Hi there,

Since I installed iOS14 and macOS Big Sur, I have encountered a problem with the Mail App using an iCloud account.

I read all my emails on my iPhone and delete most of them but it does not sync up on both my two Macs and my iPad Pro. I receive every emails on all my devices but they’re not marked as read or deleted although I did it on my iPhone.

Same for Mail on iCloud website. But if I read them on other devices than my iPhone, they’re marked as read on the iPhone and it works... This is a mystery to me.

Anyone could help me ? Have you encountered the same issus ?

Let me know, cheers !

Yannick