What is a .pstst file?

I see a handful of questions each year asking about this file. Sometimes Outlook creates this rogue file and does nothing with it, while some users report that Outlook errors report problems with a file using this extension.

After I upgraded to Office 2010, I noticed an odd file with the extension of .pstst that is not associated with any email account. I deleted the file and Outlook recreated it. How do i get Outlook 2010 to stop creating this file?

This is not a valid file and means the profile is corrupt.

The best fix is a new profile. If you don't want to do make a new profile, you can try editing the registry. Worst case scenario: you'll corrupt the profile even more and need a new profile. In my book, that makes editing the registry a worthwhile risk.

How to edit the registry to remove .pstst

1. Press the Windows key + R and type regedit and press Enter to open the registry editor.
2. Browse the registry to this key:

   HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\Outlook\9375CFF0413111d3B88A00104B2A6676 

3. Right-click on the key and choose Export to make a backup.
4. Under this key are several subkeys using the name format 0000000x, where x is a number. Each key represents an account, data file, or address book in your profile.



5. Look in each key for a value (on the right) named Delivery Store EntryID.
6. Double click to open the value and look at the bottom of the dialog for pstst.
7. If you use an IMAP account, also check the IMAP Store EID value.
8. When you find an entry with the pstst data value, delete the key from the left (0000000x). In my screenshot, this would be the key named 00000006.