Lost all old emails after installing Microsoft Office TLSC Standard 2024 with “Outlook Classic”

While Outlook 2010 is restored and displaying all the missing folders, identify and copy every attached .pst file before reinstalling Office 2024, then open those copied files directly in classic Outlook 2024.

1. Preserve the data currently visible in Outlook 2010

Do this before uninstalling Office 2010 or restoring another image:

1. In Outlook 2010, select File → Account Settings → Account Settings → Data Files.
2. Record the full location of every listed file and note which one is marked as the default. Outlook’s Data Files tab lists both .pst and .ost files with their associated accounts.^1^
3. Look for additional archive files in the folder pane. Older messages may be in a separate archive.pst, even when the current mailbox uses another data file.^2^
4. Close Outlook completely.
5. In File Explorer, copy every .pst file identified above to:
   • an external drive, and
   • a normal local folder outside OneDrive, such as C:\OutlookBackup.
   Copy the files—do not move or rename the originals. Outlook should be closed while copying an active PST.
6. Keep the AOMEI image unchanged until the copied files have been opened successfully in Outlook 2024.

For a POP account, the messages, contacts, calendar, and tasks are stored in a .pst; common Windows 10/11 locations include:

C:\Users\<username>\Documents\Outlook Files
C:\Users\<username>\AppData\Local\Microsoft\Outlook

Hidden folders and file extensions may need to be enabled in File Explorer.^3^

2. Open the preserved files in classic Outlook 2024

After installing Office LTSC Standard 2024:

1. Start classic Outlook.
2. Select File → Open & Export → Open Outlook Data File.
3. Browse to the copied .pst in C:\OutlookBackup and select Open.
4. Repeat this for every copied PST, including archive.pst files.
5. In the folder pane, expand the newly added data-file heading. It normally appears near the bottom of the folder list.^2^
6. Confirm that representative messages from several years, plus contacts and calendar items, are present before removing Office 2010 or its backup image.

Opening a PST attaches it without copying or merging its contents. This is the safest initial test and avoids duplicate messages.

3. Import only if you want everything merged

Once the copied PST has been verified, it can remain as a separate folder tree indefinitely. To merge it into another Outlook mailbox instead:

1. Select File → Open & Export → Import/Export.
2. Choose Import from another program or file → Outlook Data File (.pst).
3. Select the verified copied PST.
4. Choose the preferred duplicate handling.
5. Select the top-level folder and enable Include subfolders.
6. Choose the destination mailbox or Import items into the current folder, then select Finish.^4^

For hundreds of folders, opening the PST separately first is preferable; import only after confirming that the destination mailbox has sufficient capacity and the folder structure is correct.

If Outlook 2010 lists only an .ost

An .ost is an offline cache, not the portable master data file used for migration. For Microsoft 365, Exchange, or Outlook.com accounts, Outlook normally recreates the OST from the server; check the mailbox through webmail for the old folders.^3^

If the old folders exist only in Outlook 2010 and not in webmail:

1. While the restored Outlook 2010 profile still displays them, export them: File → Open → Import → Export to a file → Outlook Data File (.pst).
2. Select the highest folder containing the old mail.
3. Enable Include subfolders.
4. Save to a local folder outside OneDrive.
5. Copy that exported PST to external storage, then open it in Outlook 2024 using the procedure above.

Do not run SCANPST.EXE unless the copied PST fails to open or Outlook reports that the data file or folder set is damaged. If repair becomes necessary, run it against a copy, not the only preserved file; Microsoft recommends backing up the data file first.^1^

References

1. Repair Outlook Data Files (.pst and .ost) | Microsoft Support
2. Open and close Outlook Data Files (.pst) | Microsoft Support
3. Find and transfer Outlook data files from one computer to another
4. [New Outlook](https://support.microsoft.com/outlook/import-email-contacts-and-calendar-from-an-outlook-pst-file#importing-in-new-outlook-for-windows)