iCloud Mail not syncing across devices
I've been using iCloud Mail for years now. I have a MacBook Pro, iPad and iPhone 11 Pro. About 3 weeks or so ago, my email stopped syncing. All devices receive the emails, however; when I delete or read emails on my iPhone, this doesn't sync with my other devices. I haven't made any changes to my accounts to cause this, so I am at a loss. I've tried signing out of iCloud on all my devices and then logging back in, to no avail. If I go to iCloud.com and read/delete emails, then my devices will update.
Please help!!
MacBook Pro 13", macOS 10.15