Open Radar

 
Summary:
While new email sent to an iCloud email address is pushed to every device, it seems the email account is never fully synced in the background. Actions such as changes to read state and deletion of messages only seem to be downloaded from the email server when the Mail app is brought to the foreground.

The principal annoyance of this is the false unread count. It looks like I have new mail, but really it's showing the badge for messages I've already read on another device.

Steps to Reproduce:
Set up multiple (at least two) iOS devices with the same iCloud account, which has an iCloud email account.
Send an email to the iCloud email address. (From anywhere.)
Wait a few seconds for it to be pushed to all devices.
Mark the email as read on one device. (This could even be done on a non-iOS device such as a Mac.)
Optionally remove the email from the inbox.
Wait a reasonable amount of time, say an hour or more. I've tried about eight hours.
Look at the Mail app icon on a device that did not mark the email as read.

Expected Results:
There should be no badge as a result of the email that was sent.


Actual Results:
There is a badge due to the email that was marked as read hours ago. If you removed the email from the inbox and open the app at this point, you will see it briefly until the account is synchronised.


Version:
9.2 (13C75)

Notes:
Only happens with iCloud email for me. My FastMail and Google Mail accounts behave as expected.

Only tested with my personal iCloud email account. I have not actually tried with a second account because it would take ages. In a loose sense I would say this happens 'everyday'.

Configuration:
iPad Pro, iPad Air, iPhone 5S