Mail not syncing over all devices
My iMac and MacBook Air are syncing mail with each other; my iPad and iPhone are doing likewise with each other but are not syncing with the other two? There are sent emails in the iPad and iPhone which were deleted from the iMac/MacBook Air 2/3 days ago. What do I need to do to have Mail syncing on all 4 devices like it used to do. All software is up to date. All have the same Apple ID and on the same network.
iPad Air 2, iPadOS 13