Autocompletion, Exchange 2010, Microsoft, NK2, Outlook

How to Reset the Outlook Nickname Autocompletion Cache

Outlook maintains a "nickname" list that is used by both the automatic name checking and the AutoCompletion features. The nickname list is automatically compiled as you address email messages. If the nickname cache becomes corrupt, Outlook may not be able to identify recipients, may offer incorrect recipients, may send to an incorrect or old email address, or may send the message to the wrong person.

Outlook 2002/2003 and 2007 store this cache in a local, profile-specific file with the extension .nk2. Outlook 2010 changes the location of the AutoComplete Cache. It’s no longer an .nk2 file but is now a folder called Suggested Contacts within an Exchange Mailbox or a .pst file.

If you are having problems with a single recipient, you can easily delete the one cached entry as shown in the following section, To delete a single cached entry. Otherwise, proceed to the section titled To delete all cached entries below. Alternatively, you can download Microsoft 'Fix It' tool which will clear the nickname cache automatically for all versions of Outlook.

To delete a single cached entry:

In Outlook 2002/2003/2007:

  1. Open Outlook.
  2. Open a new message window, then go to the File menu and choose New > Mail Message.
  3. Type one or more letters of the recipient name or address; this will show memorized (cached) entries in a drop-down list.
  4. Use the arrow keys on your keyboard to select the entry to be deleted. With the entry highlighted, press the DELETE key on your keyboard.
    This removes the entry from your autocompletion cache.

In Outlook 2010:

  1. Switch to Contacts in the Navigation Pane.
  2. Open the Suggested Contacts folder.
  3. Find the entry you would like to delete.
  4. Right-click the contact and choose Delete.

To delete all cached entries:

In Outlook 2010:

  1. Switch to Contacts in the Navigation Pane.
  2. Open the Suggested Contacts folder.
  3. Select contacts you would like to delete. To select several entries, hold down CTRL or SHIFT on the keyboard while clicking. To select all contacts, pressCTRL + A on the keyboard.
  4. With the entries highlighted, press the DELETE key on your keyboard.
  5. Navigate to File > Options > Mail > scroll down to Send Messages > click Empty Auto-Complete list.

Alternatively, you can delete all cached entries using Outlook command-line switch. Close Outlook, go to Start > Run > type "outlook.exe /cleanautocompletecache" and hit Enter. On Outlook startup, choose your Exchange profile. It will be loaded without cached entries.

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