My boss’ PC went wacky on Tuesday afternoon and wouldn’t let him log in, so he had no choice but to shut down the computer. The computer came back up OK, but Outlook didn’t. He got a lot of weird error messages that I didn’t see, and Outlook created a new OST file on his desktop. But Outlook refused to connect to the Exchange server, and his inbox came up empty.

Like a lot of Outlook problems, the solution was the tag-team of Scanpst and Scanost. Fortunately, you don’t have to have admin rights to run them.

Scanost is the proper tool, but since the computer couldn’t connect to Exchange, it refused to run. So I resorted to running Scanpst instead, which can run locally. You can find those tools at c:\program files\microsoft office\office12\. The path varies depending on the version of Office you’re running. Office 2003 is office11. Office 2007 is office12 and Office 2010 is office13.

When you run Scanpst, it wants to know where your data lives. Typically it will be in %appdata%\microsoft\outlook or %localappdata%\microsoft\outlook. Point it at your outlook.ost file and let it fix the errors it finds. After it finishes, Outlook should connect up to Exchange normally.

The filetype that Outlook uses for storing data isn’t very robust. A Windows or Outlook crash, power failure, or improper shutdown will frequently introduce errors into the file. These problems can be cumulative. You may not notice the issue the first time you bring the system back, but eventually, you can run into the situation where Outlook launches, but can’t connect to Exchange, shows your inbox improperly, or otherwise misbehaves.
The fix is easy enough, but you have to know to do it.