According to Microsoft, active PST files from Outlook should not be placed in the One, and drive folder. They are a bit vague about why, but it seems that the synced copy may not be intact, so restoring it may create an unusable file.
No, it is not recommended to use a Cloud storage folder for your active pst-file.
How do I back up my Outlook pst file?
Try using the instructions in the How to back up .pst file data that is located on a Microsoft Exchange Server section. Select Settings, and then note the path and file name that appears. Because the .pst file contains all data that is stored in the MAPI folders that Outlook uses, the file can be very large.
Locate the desired .pst file that you found during your search. Select the .pst file, and then select OK. Type a custom name for the .pst file or accept the default name. Select OK. Select Close to exit the active window. Outlook now displays that .pst file in the Outlook folder list.
However, you can place a copy of your pst-file there, so you’ll create an on-line backup copy too. Due to the active connection and lock Outlook has on the file, One. Drive, Dropbox or something similar like Google Drive, will continuously try to upload the file and thus use a lot of network bandwidth.
Why is the pst file in outlook so large?
Because the .pst file contains all data that is stored in the MAPI folders that Outlook uses, the file can be very large. To reduce the size of the .pst file, select Compact Now in the Settings window .
Why is my Outlook data file (PST) slow to sync?
Less When you add a POP3 email account to Outlook or create archives or backup files from any of your accounts in Outlook, an Outlook Data File (.pst) may be created within your One, and drive. If this data file becomes large it can slow down your One. Drive sync and may show “Processing changes” or “A file is in use”.
How to uninstall OneDrive from Outlook?
On the Data Files tab, choose the data file location which includes One. Drive and select Remove and Yes to disconnect the file. No email data will be lost by selecting Remove, it is just disconnected from your Outlook account. It can be re-added if necessary.