In Outlook 2000, 2003, and 2007 there was always the existance of the NK2 file, which auto-completed your mail-addresses during typing in the "To" field of a new mail message. Very easy for lots of users, and often a "must have" during migrations or a profile reset. In the Outlook 2010 client, the NK2 file has completely gone, and it wil never come back, I promise you. As within the Outlook 2010 client itself, allready has been made some changes that, especially for the business markets, will change a couple of things, certainly in combination with Exchange Server 2010, and later versions. More about that in another article at a later time. So,... in Outlook 2010 the NK2 file does not exist anymore, but the "auto-complete" function" works normally, so how does that work? I'll try to explain that in this article as well as manually importing and manipulating the old NK2 file.

Outlook-2010-NK2-import-verdwenen-Oostdam.InfoIn general. What used to be the NK2 file, is now stored in a "hidden" contacts folder within your personal store. You can see an example of it in the picture here on the right. As you can see, all the names and mail- addresses a stored in a separate "contact" list, completely in line with the goal of Microsoft, to let future users, use their (shared)contacts as they should be by design. You can reach this from the "To" button in a new mail. Microsoft "hates" the NK2 file! The store is called the "Suggested Contacts", and that is exactly what it is!

Convert a NK2 file while upgrading to Office/Outlook 2010:
As the the NK2 file will not exist anymore, the upgrade proces during installing of Office 2010 will do a little tric to convert your existing NK2 file to the new format. You can find your current NK2 file on Windows XP machines on the following location:  <DISK:> \Documents and Settings \ <USERNAME> \ Application Data \ Microsoft \ Outlook; and on a Vista or Windows 7 system on: <DISK:> \USERS \ <USERNAME> \ AppData \ Roaming \ Microsoft \ Outlook. (Attention: This concerns only the NK2 files of previous versions of Outlook) During the upgrade installation proces, the "cache" for the "Auto-complete" function will be imported and the original PROFILENAME.NK2 will be renamed into the filename "PROFILENAME.NK2.OLD". At the first start of your Outlook 2010 client, the old NK2 file will be completely ignored and all changes, adding, editing or removal of mail addresses, will be stored in the new "Suggested Contacts" of your profile.

Do you wish to share youre stored names with youre colleague? Or do you want the have the same names at home? Perhaps the "auto-complete" names of your gone colleague? Or just for extra backup reasons? Maybe even back to Office 2007? (but you never want to do that!) Just copy the PROFILENAME.NK2.OLD to the location you want and rename it so, that the ".OLD" is gone and it works perfectly again under a earlier version of Outlook. (e.g. 2007, 2003, or 2000) Please keep in mind that the name has to match the exact Outlook profile name. (See also the section below)   

Are there "more" NK2 profiles present? They will be converted into"One" single suggested Contacts. So if you have had multiple profiles or your copied them, it is possible that e-mail names appear multiple times in the suggested contacts, even when your typing the address. This is a very common riddle, of which users, as well as system administrators often do not know the answer. But now you know!

Importing the old NK2 file at a new Office/Outlook 2010 installation:
OK, now you have this new fancy and fast computer/laptop, with Windows 7 as operatingsystem of course, and we installed a brand new Office Suite 2010 on it. In that case there is no earlier NK2 file present. First, copy the old NK2 file from the previous computer to the following location:  (mostly C:\) DISK:\%appdata%\Microsoft\Outlook. Appdata is of course the profile of the user we are all doing this for. The name has to be exactly the same as the profile name is. Please pay attention to that! The default name of every Outlook profile, no matter which version is "Outlook". You can check the Outlook profile name by going to: Start \ Configuration \ E-mail \ E-mail configuration \ Profile. To import the actual data from an existing old NK2 file to the "Suggested Contacts" of Outlook, make sure that the Outlook client is closed. (important) After that, go to the "Start" button and type on "Search programs and files" the following: "Outlook.exe / importnk2". plus Enter of course. Are you still using the oldfashioned Windows XP? Type the command "Outlook.exe /importnk2" on the "Run" section, and click "OK".

Tip 1: Every time you import a "old" NK2 file, the data will be (extra) added. So, if you import the same NK2 file 3 times, the names will appear 3 times in your suggested contact.

Tip 2: Within the upgrade proces, the original NK2 file is allready renamed. With a new installation this will be done the first time Outlook starts. Rename the "old" file to "old1" or "old2" etc. if you want to import other/multiple files.

Tip 3:: Make a copy of the ".old" file and put it on an external hard-disk or USB-stick. Whenever your computer crashes or your harddisk fails, you will be glad you once copied it. Read it in again,... and most of the mail addresses are back.

This article has been translated from the original dutch article that can be found at this link.


Ben OostdamBen Oostdam has been working with Windows systems since 1993. Worked for several companies as a system administrator, and is currently a Senior Support Engineer for Qurius Customer Care in the Netherlands specialized in System Center Solutions.

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