We have somebody who uses Outlook 2016, and we joined his computer to an active directory. For this, we used the ProfWiz domain migration tool to convert his local profile into a domain profile, while retaining all data. We have good experiences with this tool, and it worked flawlessly many times before.
However, for this user, we get the dreaded message similar to:
Cannot expand the folder. The set of folders cannot be opened. You must connect to Microsoft Exchange with the current profile before you can synchronize your folders with your Outlook data file (.ost).
(The German original is actually:)
Microsoft Outlook kann nicht gestartet werden. Das Outlook-Fenster kann nicht geöffnet werden. Diese Ordnergruppe kann nicht geöffnet werden. Auf die Datei 'D:\path\to\[email protected]' konnte nicht zugegriffen werden. Die Verbindung mit Microsoft Exchange muss mindestens einmal hergestellt worden sein, damit Sie ihre Outlook-Datendatei (OST| verwenden können.
We are using Office365 for Business (no local Exchange server). The only thing unusual about this user is that he has a huge .ost file (50 GB), and he thus moved it to another partition. We guess that it did not get the correct permissions when converting the PC, however this does not seem to be the case. Even after granting permissions to the new (domain) user to the file, he cannot start outlook.
There is a lot of data that is stored offline in the profile that we don't want to loose, so deleting the .ost and starting over is no option.
I cannot get into Outlook when loading the .ost to enter the password, because without logging in I cannot open the .ost... I also exhausted every option in the "Mail" control panel applet, I think.
Is there a way to fix this situation? Would undoing the domain conversion help? Could we delete everything, and then import the data from the .ost?
To avoid losing data, you can backup your mailbox to a PST file. Based on your situation, you can create a new profile. After configuring your account on new client and then import it.
Reference: Export or backup email, contacts, and calendar to an Outlook .pst file
Import email, contacts, and calendar from an Outlook .pst file