Common Outlook Start Up Command Line Switches

There are a number of command line switches for Outlook. These can be run either from a Command Prompt, or via the Run box. In all cases you need to ensure that Outlook is not running - use Task Manager to ensure that outlook.exe or anything "MAPI" is not listed. These are the most commonly used command line switches:

outlook.exe /CleanFinders
Sets Outlook 2003 Search Folders back to the default state (deletes custom Search Folders)

outlook.exe /CleanFreeBusy
Cleans and regenerates free/busy information.

outlook.exe /CleanReminders
Cleans and regenerates reminders.

outlook.exe /CleanRules
Cleans and removes both server side and client side rules. Used to clear Out of the Office rules.

outlook.exe /CleanServerRules
Cleans and removes server side rules only.

outlook.exe /CleanSchedPlus
Deletes all Schedule+ data (free/busy, permissions, and .cal file) from the server.

outlook.exe /CleanViews
Restores default views.

outlook.exe /ResetFolderNames
Resets the language of the default folders to the language of the Outlook client.

outlook.exe /ResetFolders
Restores missing folders for the default delivery location.

outlook.exe /ResetOutlookBar
Rebuilds the Outlook Bar.

outlook.exe /ResetWunderBar
Rebuilds the new Outlook Control Bar in Outlook 2003

outlook.exe /RPCDIAG
Starts Outlook with an additional window that shows the connection status of Outlook, useful for diagnosing issues with RPC over HTTPS/Outlook Anywhere. Can also be accessed after Outlook has started by holding down CTRL while right clicking on the Outlook icon in the system tray and choosing Connection Status.

Safe Mode Rules

Useful for getting Outlook to start when there are problems. Not all variants apply to all versions.

outlook.exe /safe Starts Outlook without extensions, the Reading Pane, or any toolbar customization.
outlook.exe /safe:1 Starts Outlook with the just the Reading Pane off.
outlook.exe /safe:2 Starts Outlook without checking for mail at startup (good if you have a bad message in the mailbox) - also /nopollmail
outlook.exe /safe:3 Starts Outlook with extensions turned off, but listed in the Add-In Manager (usually addins aren't listed)
outlook.exe /safe:4 Starts Outlook without loading Outcmd.dat (customized toolbars) and *.fav file.

More Information

Full List of Outlook 2003 Command Line Switches: http://office.microsoft.com/en-us/outlook-help/command-line-switches-HP001003110.aspx 
Full List of Outlook 2007 Command Line Switches: http://office.microsoft.com/en-us/outlook-help/command-line-switches-for-microsoft-office-outlook-2007-HP001218589.aspx 
Full List of Outlook 2010 Command Line Switches: http://office.microsoft.com/en-us/outlook-help/command-line-switches-for-outlook-2010-HP010354956.aspx