I have a new Blackberry Classic synched to Outlook via my company's BES. All emails read in Outlook do not update as read on the device. However, emails read on the device are marked as read in Outlook.
This used to be managed under the Email Reconciliation settings of the older models, but I haven't been able to find what governs this in OS10.3.2. (There is a separate setting related to deleting emails, but not marking them as read).
BlackBerry 10 uses Active Sync which is much different than the legacy BlackBerry and BES.
I would ask your BES admin to remove (for 5 min or more) and then re-add the email profile to your account within BES10 /12
Once they put the email profile back, test by sending yourself and email or two.
If it still doesn't work, id enroll another new BlackBerry (or an active sync device) again your profile and see if the issue follows you to the new phone. If it does, it's likely Outlook and others are having similar issues.
There are a many assumptions here about your BlackBerry 10 OS, bes10/12, exchange settings and how it's all set up...so I reserve the right to be wrong :)