How to Import NK2 Files into Outlook: A Comprehensive Guide

Microsoft Outlook, a staple in email communication for both personal and professional use, relies heavily on its auto-complete feature. This feature, which remembers frequently used email addresses, significantly speeds up the process of composing new messages. In older versions of Outlook (pre-Outlook 2010), this data was stored in an .nk2 file. However, with the introduction of Outlook 2010 and subsequent versions, the auto-complete data is now stored in a different format, making the direct import of .nk2 files no longer supported. This change can be frustrating for users who have upgraded and wish to retain their previously saved contact suggestions. Fortunately, there are methods to transition your .nk2 data into a format usable by newer Outlook versions. This comprehensive guide will walk you through the various techniques to achieve this.

Understanding NK2 Files

Before diving into the import process, it’s crucial to understand what NK2 files are and why they’re not directly compatible with newer Outlook versions.

• What is an NK2 File? An NK2 file is a proprietary Microsoft format used by older versions of Outlook (2003, 2007 and older) to store the auto-complete name list. This file essentially acts as a database of recently used email addresses, allowing Outlook to suggest them as you type in the “To,” “Cc,” or “Bcc” fields.
• Why the Change? Outlook 2010 and later versions store auto-complete data in a hidden folder within the user’s mailbox data file (PST or OST file). This change was implemented to make the auto-complete functionality more robust and synchronized across different devices where the same Outlook account is used. It also simplifies the management and backup of user settings.
• Why is NK2 Import Needed? Users who have been using older Outlook versions for an extended period often have a significant number of entries stored in their NK2 files. Manually re-entering all these email addresses can be time-consuming and tedious, making the transition process frustrating. The need to import or convert this data remains strong for users migrating to newer versions of Outlook.

Methods for Importing NK2 Data into Outlook

Although direct .nk2 file imports are not supported by newer Outlook versions, you can effectively transfer your auto-complete data using the methods described below.

Method 1: The Rename Trick (For Outlook 2010 and Sometimes Outlook 2013)

This is the simplest, but also the least reliable method. It relies on Outlook 2010’s ability to sometimes recognize the NK2 file when placed in the correct location and renamed to match the new auto-complete file’s name. This method is not guaranteed to work, especially with later Outlook versions, but it is still worth trying first.

1. Locate Your NK2 File:
   • By default, your NK2 file is usually located in the following path (you will need to replace USERNAME with your Windows username):C:\Users\USERNAME\AppData\Roaming\Microsoft\Outlook
   • The file will be named Outlook.nk2 or profilename.nk2 (where profilename is the name of your outlook profile).
   • If you don’t see the file at this location, search for files with the extension “.nk2” using Windows File Explorer.
2. Locate the Auto-Complete Stream File in newer Outlook:
   • Close Outlook completely.
   • Press Win + R to open Run dialog
   • Type: %localappdata%\Microsoft\Outlook and press Enter
   • Look for a file with the extension .dat. The name usually follows the pattern: RoamCache or Stream_Autocomplete_xxxx_xxxxxxxxxxxxxxxxxxxxxxxx.dat
   • Make a copy of this file to backup it.
3. Rename the NK2 file:
   • Rename your NK2 file to match the name of the new autocomplete file in the above step.
   • For example if the new file is Stream_Autocomplete_0_72F7C9C988B15649B8539D8167F05F5A.dat, rename the nk2 file to the same Stream_Autocomplete_0_72F7C9C988B15649B8539D8167F05F5A.dat
4. Replace the Auto-Complete Stream File:
   • Move or Copy your renamed nk2 file to the location where you found the current autocomplete file (%localappdata%\Microsoft\Outlook)
   • Confirm if you are asked to overwrite the existing file.
5. Start Outlook:
   • Start Outlook and compose a new email.
   • Test if the auto-complete suggestions are loaded.
6. Troubleshooting:
   • If this method doesn’t work, restore the backup of your .dat file and try the next method.

Why this Method Sometimes Works: This method leverages the internal logic of Outlook which, in some cases, can still read and interpret the NK2 format. By tricking Outlook into thinking the .nk2 file is the new auto-complete data file by renaming it, you might be able to transfer the data. However, this is often unreliable, especially with newer updates and versions.

Method 2: Using an NK2 to Auto-Complete Conversion Tool

For a more reliable approach, consider using a dedicated NK2 to Auto-Complete data converter. Several third-party tools are available that can effectively read your .nk2 file and convert its contents into a format that can be imported into newer Outlook versions. Some popular tools are:

• NK2Edit (Free): A popular free tool specifically designed to read, edit, and manage the contents of .nk2 files. It can be used to export NK2 data to a CSV file which then can be imported to contacts.
• Other Commercial tools Several commercial tools are also available that offer more features and support for other versions. A google search for ‘nk2 to autocomplete converter’ will bring a list of these tools.

Here’s a general outline of the process using NK2Edit (the process is similar for other tools):

1. Download and Install NK2Edit:
   • Download the free NK2Edit tool from a reputable source.
   • Follow the installation instructions provided by the software.
2. Load Your NK2 File:
   • Launch NK2Edit.
   • Go to ‘File’ -> ‘Open’ and locate your NK2 file.
3. Export the data to CSV:
   • Select all entries in the NK2edit interface.
   • Go to ‘File’ -> ‘Save Selected Items’ and select ‘CSV File (*.csv)’
   • Provide a name and location to save the CSV file.
4. Import Contacts in Outlook from the CSV file:
   • Open Outlook and go to ‘File’ -> ‘Open & Export’ -> ‘Import/Export’.
   • Select “Import from another program or file” and click ‘Next’.
   • Choose “Comma Separated Values” and click ‘Next’.
   • Browse and select the CSV file you created with NK2Edit.
   • Choose how you want to handle duplicates and select ‘Next’.
   • Select the “Contacts” folder as the destination for the import and select “Next”.
   • Click “Finish” to start importing your contacts.
5. Update the AutoComplete Cache:
   • After importing the contacts, it may take a little time for the autocomplete cache to be updated.
   • Try to use some of these imported email addresses in new emails to force Outlook to include these in the auto complete cache.

Why This Method Is More Reliable: These tools are designed to accurately interpret the structure of NK2 files and convert the data to a more universally recognized format (like CSV), which can then be used to import contact entries into Outlook. Using this method provides a more robust way to get your auto complete contacts back into new versions of Outlook.

Method 3: Manually Recreating Auto-Complete Entries (As a Last Resort)

If all other methods fail, you may need to manually re-create the auto-complete entries by sending emails to each contact one-by-one. This method is, of course, the most time-consuming and frustrating. You’ll have to manually type each email address and send a test email. This will prompt Outlook to add the email address to your auto-complete list.

1. Open Outlook:
   • Launch your new version of Outlook.
2. Create a New Email:
   • Start a new email message.
3. Add Entries Manually:
   • Manually type each email address you want to add to the auto-complete list into the “To”, “Cc”, or “Bcc” field.
   • Add any subject and short message body and send the email.
4. Repeat:
   • Repeat this process for all contacts you want to re-add to your auto complete list.

Why this method should be avoided if possible: This method is incredibly time consuming and error-prone, making it the least desirable approach. It is best to try other methods before resorting to this one.

Important Considerations and Tips

• Backup Your NK2 File: Before attempting any method, make a backup of your .nk2 file. This ensures you can revert to the original data if something goes wrong.
• Outlook Version: The specific steps might vary slightly depending on your Outlook version. Refer to the documentation of your specific version if you encounter issues.
• Third-Party Software: When using third-party tools, ensure you download them from a reputable source to avoid malware or viruses.
• Patience: Importing the auto-complete data may take some time, depending on the size of your .nk2 file. Avoid interrupting the process and allow it to complete.
• Clear the Auto-complete Cache: To force Outlook to re-import all addresses, you can clear the auto-complete cache from within the Outlook Options settings.
• Test Auto-Complete: After importing the data, test the auto-complete feature by composing new emails and checking if the suggested addresses appear as expected.

Conclusion

While the transition from older versions of Outlook that used .nk2 files to newer versions with different auto-complete mechanisms can be challenging, it’s certainly not insurmountable. By following one of the methods outlined above, you can effectively transfer your auto-complete data to your new Outlook, saving you a significant amount of time and effort. Whether you prefer the sometimes functional rename trick, the more reliable converter tool method, or even, as a last resort, the manual entry method, you have a variety of ways to make the import process successful.

By carefully following these instructions, you can successfully retain your frequently used email addresses and enjoy a seamless experience with your new Outlook version. Remember to backup your NK2 file before you start to protect your valuable data.