How to clear the AutoComplete list in Outlook 2010

May 4, 2010

in Microsoft, Office, Outlook

Outlook 2010 introduced a change to the way the AutoComplete list (aka: nickname cache) is stored on the client.  The new Roaming AutoComplete list is now stored on the Exchange Server. A user’s recipient AutoComplete list is now available to any computer on which Outlook 2010 runs that is connected to the same Exchange account. Individual names can be easily removed from the list by using the new inline Delete function.  Just simply type the first few characters of the name you wish to delete and press the Delete key or click the X.


What this means for you is that your AutoComplete list is synchronized between platforms: OWA, Windows Mobile and Outlook will all share the same AutoComplete list.  While this sounds up front like a great enhancement there are some changes that you need to be aware of in case you need to clear this list.

First, there is no more NK2 file.  The actual file you are looking for is located is:


Deleting this file will not clear your AutoComplete list.  As soon as you start Outlook 2010 the file will reappear, along with any bad addresses.  So how does one clear the entire list?

Use one of the methods listed below to reset the Outlook nickname cache for Microsoft Outlook 2010.

Method 1

  1. With Outlook 2010 open, click File (BackStage), and then click Options.
  2. Click the Mail tab.
  3. Under Send Messages, click Empty Auto-Complete List.

Outlook will generate a new nickname cache.

Method 2

  1. Click Start, and then click Run.
  2. Start Outlook by using the /CleanAutoCompleteCache switch.
    For example: Outlook.exe /CleanAutoCompleteCache
    Note If Outlook is not installed in the default location, you will need to point to the path of Outlook.exe.

Outlook will generate a new nickname cache.

Reference KB287623 for more information…

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Niclas Winsa June 2, 2010 at 9:23 am

Thanks, yot made my day a better day !
If I understand correctly this is going to be roamed from server in exchange 2010 ?
That means we can fix this for our users centrally. Or ?

Matt_Wade June 21, 2010 at 7:00 pm

Apologize for the late reply. No you will still not be able to manage the Autocomplete list centrally. That would be a nice option for future versions of Exchange.

Judie Rahman June 24, 2010 at 2:09 pm

Matt – Great article! Will this work if we are running Exchange server 2007? Or do we have to wait for 2010?

Matt_Wade June 25, 2010 at 6:58 pm

Yes, this still applies if your are running Outlook 2010 on Exchange 2007.

Matt_Wade September 7, 2010 at 3:27 pm

I haven't tested that particular functionality, but I imagine that the client would behave the same regardless of which version of Exchange is on the backend. What you would lose is the share nickname cache between the different clients.

junaid April 27, 2011 at 4:14 am

dear how can i reverse this process. i need to include names in auto complete list. need your suggestion.

david June 21, 2012 at 2:36 pm

Is there a way to stop the auto complete list from sorting based on usage?

Matt July 10, 2012 at 9:33 am

I haven’t found any way to change the default behavior of the Autocomplete feature.

Mohd Arif November 9, 2012 at 7:13 am

If you want to clear your outlook’s temp cache, then ran the command ” Outlook.exe /CleanAutoCompleteCache “.
But always remember if you do not save your address book of outloo,you will loose it. save adddress book first and then ran this.

Thank You,

Sherrie November 29, 2012 at 12:45 pm

I assume you then need to import your address book back into Outlook.

I have tried these steps before, but haven’t got autocomplete to work. We sill receive the error. I am following your instructions once more, doing the clear autocomplete within Outlook, then running the autocomplete clear cache option. I hope this works. I have a very frustrated user who I would love to make happy.