It seems that you are experiencing limitations with flagged messages in Classic Outlook and the management of PST files with the new Outlook. Currently, new Outlook does not support the same functionality for PST files as Classic Outlook, which might be affecting your ability to access them. Additionally, the visibility of flags on messages in new Outlook is designed to show the flag only when hovering, which differs from the previous behavior you are accustomed to.
Regarding the follow-up flag timing feature, it is noted that certain functionalities may be missing or altered when switching to IMAP in Classic Outlook. Unfortunately, there may not be a direct setting to revert these changes in the new Outlook.
For more detailed guidance on managing PST files and understanding the differences in policy settings between Classic and new Outlook, you may want to review the relevant documentation provided by Microsoft.
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