Sometimes, the follow-up folders for some users are missing after the .pst import. Please use the following procedure to locate these folders.
1. Right-click your search folders item.
2. Click New Search Folder.
3. Click Mail flagged for follow up. This will add the folder to your search folders list.
Note: Once the follow-up folder has been created, it may be added to your favorites. It will display in the top of the mail. Right-click the search folder and click Add to favorites.