Q: What are the "clean" command-line switches in Outlook 2010?

A: Microsoft Outlook includes a set of command-line switches that let you perform various tasks, from troubleshooting issues by resetting some aspect of Outlook to its default, to launching a specific component of Outlook, such as a new appointment form. Outlook 2010 added a series of "clean" command-line switches to help manage Outlook caches. In addition to "clean" switches already present in Outlook 2007, such as /cleancategories, /cleanclientrules, and /cleanroamedprefs, Outlook 2010 adds a few unique to its version: /cleanautocompletecache, /cleanfromaddresses, /cleanconvongoingactions, and /cleansharing. For a complete list of Outlook switches, please see the Microsoft article "Command-line switches for Outlook 2010."

Outlook caches a lot of input content to provide a more efficient user experience. Microsoft added several new command-line switches to Outlook 2010 that purge content in local caches within Outlook profiles. These new switches all include the term clean in them, which, as it suggests, removes content from caches identified by the switch. Let's take a look at how you would use the /cleanfromaddresses switch.

When you send an email message from Outlook, but manually change the From address for the message to something other than your account's default address, Outlook saves that address in a cache in the profile on the local workstation, similar to the Outlook nickname cache used in recipient fields. The From Address cache maintains addresses from user input and doesn't discriminate; that is, it also saves erroneous human input. When you open a new message in Outlook, you can select the From button, which opens a drop-down menu. At the bottom of that context menu, you can select Other E-mail Address to open the input window that Figure 1 shows.

Figure 1: Entering a different From address in Outlook 2010

For accounts that authenticate to an SMTP server (e.g., IMAP or POP), users could potentially change the From address to anything that adheres to the standard SMTP address format. Outlook caches those addresses for easy re-use in another message. Figure 2 shows an example with cached addresses shown in the drop-down menu in a new message.

Figure 2: Cached From addresses in the drop-down menu in Outlook 2010

As the name command-line switch suggests, you execute this switch as an option for the outlook.exe executable. The /cleanfromaddresses switch removes all content stored in this cache:

c:\Program Files\Microsoft Office\Office14>outlook.exe /cleanfromaddresses

If you have the 32-bit version of Office installed on a 64-bit Windows OS, the path would show the x86 path for program files:

c:\Program Files (x86)\Microsoft Office\Office14>outlook.exe /cleanfromaddresses

The command launches Outlook 2010 and performs the requested action of the switch during startup. The same principle extends to the other "clean" command-line switches for outlook.exe. For example, to clear the nickname cache, you would launch outlook with the /cleanautocompletecache switch at the command line. For this and other "clean" command-line switches to work, you must exit Outlook 2010-and wait so that outlook.exe is no longer in the list of processes in Task Manager-before executing the command-line option.

Also, as of this writing, the command-line switch for /cleanfromaddresses is listed in Microsoft's documentation as /cleanfromaddress. This switch needs to be plural to avoid the error "The Command Line argument is not valid. Verify the switch you are using."

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.