I fixed a little annoyance today, and since the fix was easy, I'm almost certain to forget it without writing it down.

I've been using Outlook 2010 with IMAP folders for some time. Trouble is, Outlook actually maintains a local depository, a special PST file located in C:\Users\<username>\AppData\Local\Microsoft\Outlook. If you have lots of messages on the IMAP server, this file can become quite large. In my case, since I actually used Outlook to populate the server with messages from over 15 years' worth of archived Exchange/Outlook files, this PST grew to a 14 GB monster.

First, so long as the messages are actually present on the server, this file is safe to delete. Or move. The next time you start Outlook, it will just re-create the file.

Second, it is actually possible to force Outlook to use another location for this file, by creating the Registry entry HKCU\Software\Microsoft\Office\14.0\Outlook\ForcePSTPath.

Thanks to slipsticks.com for the tip.