After promoting our Exchange to a DC we receive the Unable to attach to Mailboxes error. If I restart all the BE services, the backup will succeed but fail the next day unless the services are restarted. Any advice on this will be highly appreciated. Thanks
Agree with CraigV, but I guess you've already done this. Anyway if it doesn't help,
stop BE services, remove the BE account from all groups other than Domain Admins, and restart the services and see how it goes.
Run the BEutility.exe, and then into All Media Servers (right-click) --> Change Service Account.
Put in the same details that you currently use, and let the system restart your services.
Try again...
Agree with CraigV, but I guess you've already done this. Anyway if it doesn't help,
stop BE services, remove the BE account from all groups other than Domain Admins, and restart the services and see how it goes.