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Managing Microsoft Outlook's AutoComplete option

Discover freeware for Microsoft Outlook's AutoComplete option that lets you manage, edit and delete AutoComplete data and troubleshoot corrupt .NK2 files.

The AutoComplete option in Microsoft Outlook 2003 and 2007 is a dropdown email address list that stores its data in an .NK2 file. Microsoft doesn't provide a native tool for accessing this file, but there is a freeware utility called NK2View you can use to manage, edit and delete AutoComplete email information.

Microsoft Outlook's AutoComplete feature automatically populates email addresses in the "To" and "CC" fields. If you begin to type the name of a commonly used addressee, AutoComplete will make a best guess as to the name you're typing and provide several suggestions in a dropdown list.


The AutoComplete dropdown list is editable -- i.e., you can normally navigate the list using the up/down arrows or use the Delete key to remove entries. But if the AutoComplete dropdown address list becomes corrupted, the list needs to be deleted before the feature will behave properly.

The .NK2 file houses Microsoft Outlook's AutoComplete data, but Microsoft doesn't provide a native option for accessing this binary formatted file.

Luckily, programmer Nir Sofer, author of a host of truly amazing utilities, has created a tool called NK2View that fills this functionality void.

NK2View requires no installation -- you can unpack it and run it from any directory. When run, it reads the .NK2 file for the current user's Microsoft Outlook profile and displays it in a grid, which can be exported to a variety of file formats (HTML, plaintext, etc.). Each display name and email address can be inspected in detail, edited or deleted. You can even add items from your Microsoft Outlook address book to the AutoComplete dropdown list.

More on Microsoft Outlook:
How to delete unwanted 'nicknames' in Microsoft Outlook

Resetting the Microsoft Outlook AutoComplete 'nickname cache'

The Microsoft Outlook Toolbox

More Microsoft Outlook troubleshooting tips and tutorials

If you want to open another .NK2 file somewhere else, you can; you're not limited to just the .NK2 file in the current user's email profile. It also doesn't matter which computer the .NK2 file resides on or where it was copied from.

The AutoComplete utility is also available in several foreign languages, including French, German and Italian.

Note: Under Windows Vista, you do not need to run the program as an administrator to see an .NK2 file for the current user, but it doesn't hurt to run it as an admin anyway.

About the author: Serdar Yegulalp is editor of Windows Insight, a newsletter devoted to hints, tips, tricks, news and goodies for all flavors of Windows users.


If you have a distribution group (accessible from the AutoComplete feature) and then the distribution group is updated, will it update in AutoComplete as well? Is it different for distribution groups in the "Contacts" list versus the main address book? We ran into some quirky things with this late last year.
—Jim S.


I did a bit of digging and from what I can tell, the AutoComplete item is not updated if a distribution group name is changed. Microsoft documented this problem in its article The AutoComplete feature displays an incorrect email alias for a distribution list in Microsoft Outlook.

Without actually trying this myself, I suggest deleting the distribution group from the AutoComplete cache when a distribution group changes. After you use the correct distribution group name in a To: field, it should be re-added correctly.

If anyone has any experience with this problem, please share your solution.
—Serdar Yegulalp, tip author


I don't think this tip applies to Microsoft Outlook 2000 (I'm not sure about other versions of Outlook since I don't have them). There is no AutoComplete option in Outlook 2000. There is a similar feature called "Check Name" that is used in Outlook 2000. However, it is only available in the Corporate and Workgroup mode, and the suffix of the file is .nick. I thought you'd want to modify the tip to indicate the various versions of Outlook/Outlook Express to which it applies.
—Terry M.


Yes, you are correct. The AutoComplete option applies to Microsoft Outlook 2003 and 2007. Thank you for pointing that out. We've specified this information in the tip summary at the top of the page.
—Serdar Yegulalp, tip author

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