A user wanted to know how to move their auto-complete list to a new account in Outlook:
We're switching from Google Apps to Office 365. Can we migrate auto-complete addresses to the new accounts? We don't have an NK2 to import.
The auto-complete list for Outlook 2010 and newer is stored in .dat files in the RoamCache folder under the Local AppData folders. You can access this folder by typing or pasting the following command into the address bar of Windows Explorer and pressing enter.
You can use a utility to extract the addresses from the auto-complete stream and insert them into the new auto-complete stream. Or you copy and rename the .dat file with the name of the .dat file used by the new account.
In Outlook 2007, the autocomplete list is stored in a file with the extension NK2. If you are moving from Outlook 2003 or 2007, you'll need to import the NK2. When you upgrade in place, the NK2 should be imported automatically. If you get a new computer, copy it to the same location on the new computer and start Outlook using the /importnk2 switch.
Auto-Complete Cache Editing Tools
Open source project to read MS Outlook autocomplete (NK2) files and extract email addresses. Beta version 0.5
Use NK2Edit to edit or delete information stored in the NK2 file or Outlook 2010/2013's Autocomplete Stream, including the display name, the email address, the exchange string, the Drop-Down display name, and the search string. Free for home use; Commercial license available.
Use NK2View to view, edit or delete entries in Outlook's .NK2 AutoComplete file. Export the records to text, html, or xml files. Freeware. Version 1.37