PST stands for Personal Storage Tables. When they get too big they often get corrupted, leading to errors. They can, however, be fixed. It isn't incredibly difficult, but you still want to make sure the other two methods didn't work first. They are simpler and less invasive. That said, using a PST repair program is not very difficult, and is generally safe. Even better, Microsoft bundles a repair program right with Outlook called Inbox Repair., For Windows Users, you may have a program called "Scanpst.exe" that will do this for you. For Mac users, you may not have the option to use Scanpst. In this case, you must go search online to download an "Outlook PST Repair" program.


Sites like CNET have Outlook PST Repair programs for free.
Scanpst is sometimes hidden. To find it, copy the following into a search bar: Program Files\Microsoft Office\. Then click OFFICE and scroll to Scanpst., Head back to the Account Settings (either through Tools or File → Info) and click on the tab labeled "Data Files." You'll see a list of all your email address. Click the one with the issue and then select the button "Open File Location." This will open a window showing your .pst file on your computer.\


Remember this location on your computer -- you'll need it later.
 Now that you know where it is, click on "Browse" or "Load PST" and cue up your Outlook file. On some programs, you may be able to just click and drag it over from your old file.
 The first step is a scan of your PST files. More likely than not, it will then offer to repair them. Click "Repair" to fix up your old file, which should prevent any further issues.


Repair will automatically create a backup of the PST file, so don't worry about losing old data., Once you've repaired your old file, simply drop it next to the old one. Remove the broken file, putting it in a new, separate folder for safe keeping in case something went wrong. If you're having trouble syncing up the new file, simply return to the "Data Files" screen in Account Settings. From there, you'll find the button "Add File" on the left-hand side. Click it to add your new PST file.


Leave the folder containing your PST files open while working. This will make it much easier to find later on.
Try the previous two methods before attempting a PST fix.
Open your PST repair program.
Open Outlook to find the location of your PST files.
Return to your PST repair program and locate the .pst file you just found.
Hit "Start" and follow the on-screen instructions.
Open Outlook with the new PST file.
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