“One of my email contacts has a new email address as their company changed their domain name. I have deleted and re-entered her correct email address about half a dozen times in the address book and yet my PC still thinks I am sending her emails to her old domain.com instead of her new domain.com . When I entered her name it defaults to the “olddomain.com” address even though it is nowhere to be found on my PC. I have to select her “newdomain.com” address from the address book for it to work. Has anyone experienced where Outlook is keeping this old email address info? How can I can purge it?”

This is an all too common experience for many users.

If you are using Outlook 2002, 2003, 2007, or 2010, use the arrow key to select the incorrect address and press the Delete key. You can clear the entire autocomplete file (*.NK2): in older versions you need to delete the NK2 file from your hard drive, while Outlook 2010 has a clear cache button in Options (screenshot below).

Older versions of Outlook store nicknames in a file using the extension *.nick but do not support using it for autocomplete.

The nickname files (.nk2) are found at C:\Documents and Settings\username\Application Data\Microsoft\Outlook if you are using Windows XP/2000 or C:\Users\username\Application Data\Microsoft\Outlook. You can easily access it by pasting

%USERPROFILE%\Application Data\Microsoft\Outlook

in the Address bar of your browser or Windows Explorer. Close Outlook then delete or rename the NK2 file. When you restart Outlook it will create a new, empty NK2 file.

Outlook 2010

Outlook 2010 does not use the NK2 file; it stores the autocomplete cache in the mailbox or data file. Outlook 2010 also creates a contact for people you send mail to, as insurance if the autocomplete cache becomes corrupt. Look for these contacts in the Suggested Contacts folder.

Clear the autocomplete cache using the File, Options, Mail, Empty Auto-complete list button.

If addresses are not saving in the autocomplete list between Outlook sessions, you may need to delete the RoamCache file. Instructions are at  Outlook 2010 doesn’t save Autocomplete.

See Suggested Contacts and Auto-Complete Lists to learn more about Outlook 2010′s autocomplete cache and suggested contacts.

Nickname cache is empty

“We use Outlook and my users aren’t very good at adding email addresses to the Contacts folder and rely heavily on the autocomplete cache, but it gets replaced often. Why does it seem so fragile?”

If the users are losing addresses of people they recently replied to (but not older addresses), it’s because Outlook crashes or does not close properly and the changes are not written to the NK2 file. The existing *.NK2 shouldn’t be replaced by a clean *.NK2 if this happens, but new addresses you’ve sent new mail to or replied to won’t be saved to the file. Less used addresses are replaced by new addresses when the NK2 contains 1000 addresses in Outlook 2003 or 2000 address if using Outlook 2007.

If all addresses disappear, it means something is corrupt and Outlook is replacing the NK2 with a new, clean one.

See OUTLOOK.EXE continues running after you exit Outlook

If you’re using the autocomplete cache as your address book because it’s too much effort to right click on an address and save it as a new Contact, you should use a utility that creates contacts from all addresses you reply to, as the autocomplete cache is not a good substitute for contacts.

Use the nicknames with new profiles

If you create a new profile you can copy the NK2 file used by your old profile. You’ll need to rename it so it matches the name of your new profile.

How to clear names from the cache

To remove single addresses, select the name using the arrow keys then press Delete. In Outlook 2010, you can also click the x beside the name to delete it.

To remove all of the addresses, either delete the NK2 file (at %USERPROFILE%\Application Data\Microsoft\Outlook ) or go to Tools, Options, Email Options, Advanced Email Options and deselect the option to suggest names near the bottom of the dialog.

In Outlook 2010, clear the cache from the File, Options, Mail dialog.

Remove an Address from the Auto-Complete Cache Tutorial

Delete Autocomplete entries

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Auto-Complete Cache Editing Tools

Tools

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Last reviewed on Dec 8, 2011