MS Outlook® Autocompletion


By: The Tech Guy

A short note about this document. This document was not intended to be an advertisement for our software, but rather an attempt to unravel some of the mysteries surrounding the autocompletion feature.

The Autocompletion feature defined In MS Outlook® XP the autocompletion feature begins to function after typing three characters in the “TO”, “CC” or “BCC” field of an outgoing e-mail. In Outlook® 2003 autocompletion begins suggesting names after typing one character of either the Name or the Alias. Autocompletion does NOT attempt to find a name or e-mail match located in one of your Contact folders. Autocompletion searches the Autocompletion database file known as the NK2 file. The NK2 files also store data other than just the name and alias. Other information stored inside of the NK2 file are the actual record Type: (SMTP, EX, FAX, MAPIPDL,etc), Name (Individuals Name if present), Alias (SMTP address or GAL reference) and Exchange information (X500 or DN address). An alias is either an address used to identify you to either your ISP or Exchange server. Therefore an alias can be an address like or it can be an identifier used by your Exchange Server like Jdoe. The latter is nothing more than a reference in a Global Address List (GAL) which identifies you in a database. The latter reference to an alias in an NK2 file is important to understand because the NK2 file also stores the entire X500 (Distinguished Name) address. The X500 or Distinguished Name stores information so that the Exchange Server will know how to process your e-mail. When an Exchange administrator changes the information about an individual on the Exchange server, this change is NOT reflected in the NK2 file. This creates e-mail problems. Let’s say that your Exchange server is located at Site A. Then, due to system consolidations or upgrades the server is moved to Site B. The GAL knows that jdoe is now on Site B, but the NK2 file still contains a reference to your former server location of Site A. Consequently, when a user attempts to send an e-mail to jdoe, autocompletion will load the erroneous DN information and your e-mail will probably not be delivered. This problem accounts for many undelivered e-mails in today’s corporate Exchange environment. It is important to understand however that the NK2 database functions like many other databases. In the case of Autocompletion, it will only find words or names in the first field of the name or Alias field. It will also find a match on the entire e-mail address field as it is only one word in length.

In the example below for instance, typing the letter “D” will not produce an Autocompletion if you are trying to find John Doe’s record. MS Outlook® parses the Name field and only searches the first part of the record. In order to get the record below to autocomplete you would need to either type the letter “J” or the letter “S”. The letter “J” would find the word John and typing the letter “S” will find the Salesmanjoedoe e-mail address.

Correcting or removing unwanted entries in your autocompletion cache Occasionally you will inadvertently enter a recipient’s name incorrectly into the autocomplete cache. Realizing your mistake you re-type the recipient’s name correctly forgetting about the old, incorrect entry.  Then the next time you autocomplete that recipient’s name you run the risk of autocompleting the wrong entry!  The fix for this type of problem is very simple.  Inside of Outlook, when you begin typing that recipient’s name, you will notice a drop down list appear.  Scroll down and highlight the unwanted entry and press the delete button.  This will permanently remove the unwanted entry from the autocomplete cache.

By default, Autocompletion is turned ON. This feature can be selected by navigating to: TOOLS>OPTIONS>PREFERENCES, TAB>E-MAIL OPTIONS>ADVANCED E-MAIL OPTIONS. Check or uncheck the box to the Suggest Names while completing the TO:, CC, and BCC fields as indicated below.

Autocompletion vs. Autoresolution Many individuals confuse Microsoft Outlook’s Autocompletion functionality with Autoresolution. It is easy to understand how this might happen. Autoresolution attempts to match the first few letters typed into a new e-mail address with entries stored in a Contact folder that is registered with your Outlook profile. The Autoresolution function is turned on or off at the same location as autocompletion. That function is enabled/disabled by selecting the checkbox next to “Automatic name checking”. Autocompletion attempts to match the first characters typed in a new e-mail address with entries stored in the NK2 file (autocomplete cache). Autocompletion DOES NOT try to match typed entries that are contained in a contact folder.

Profiles MS Outlook uses Profiles to manage different e-mail settings on one computer. For each Outlook Profile created, Outlook will create an NK2 file. Most people only use a single profile, but some users, especially laptop users, may opt to use different profiles, one for remote use and one while connected to a LAN at the office. Profile management can be found in the Control Panel under Mail. Select “Show Profiles” to open your Profile Manager.

When the first Profile is created, the default Profile name is “Outlook”. As stated earlier, each Profile will create an NK2 file to be associated with it. The NK2 file will bear the same name as the Profile. Thus in this example, the NK2 file would be called Outlook.NK2. Generically, this is reflected as <Profilename>.NK2.

Migrating your NK2(s) file to a new machine Oftentimes people purchase new PC’s and install all new software only to find that their Outlook is no longer autocompleting.  The cause of this is because while most data may have been ported from the old machine to the new, one usually forgets to migrate the NK2 file.  In the paragraphs that follow, we have attempted to provide detailed instructions moving these files.  Before beginning, we want to reiterate a few basic facts about the NK2 file.

  • First, the NK2 file name is YOUR OUTLOOK PROFILENAME.NK2.
  • Second, there is one NK2 file for each Outlook profile.

To determine your profile names you will need to go to your Control Panel.  See screen print below:

Double click the Mail icon and press the Show Profiles button.

This will generate a window reveal your profile name(s).  Most people have only one profile, however, you’ll want double check here to determine all possible profile names in existence on your computer.  In the example below, note that only one profile name exists, Outlook.

In order to copy this file from your computer to another computer you must first be able to find it.  Because this file is a hidden, system file you will first need to make some changes to the way that your computer displays hidden and system files.  To make these changes to your system you will need to open Windows Explorer (NOT Internet Explorer), then go to Tools > Folder Options > View tab until you see a page that looks like the one below.

In this window you will want to select the option to Show hidden files and folders and Uncheck the option to Hide protected operating system files. This will enable you to view hidden and system folders and file like the NK2 file.

Now that you can “see” these files, we must navigate to them so that they can be copied.  (We recognize that there are several ways, including some shortcuts for this task, but we are taking the long road to improve comprehension.)

Within Windows Explorer (Start > All Programs > Accessories > Windows Explorer) you want to begin with your C: Hard disk drive.

Proceed to the following path:

  1. Documents and Settings

  2. User login name (the name you use to login to your Window’s session)

  3. Application Data (this should be lighter than the other folders because it is a system folder)

  4. Microsoft

  5. Outlook

Now that you have located your NK2 file(s), right click on each one and select the copy function. This will make a copy of your file(s) and place them into your computer’s clipboard.  You now need to paste or copy these files to the appropriate location on your new computer.  There are several ways to copy these files, but the easiest way is just to copy them in an email and email the files to yourself as an attachment.  You may also copy them to a thumbdrive, floppy disk, or some other removable media.

Once you have your autocomplete file(s) copied, you must now save it into the same location on the new computer.  Remember to modify your folder view options on your new computer this will make this process much easier.

Once the file is copied into the appropriate location on your new computer, make a backup!  We’d suggest just copying and pasting the folder in the same directory.  This will make a file called “Copy of profilename.nk2.  Next, you will want to determine the Outlook mail profile name on the new computer.  Whatever the profile name is, rename your NK2 file to that name.  Example, let’s say that the new profile name is “Outlook Network”.  If you want your newly copied NK2 file to work with that profile, just rename your NK2 file to outlooknetwork.nk2.  

Exit out of all folders, launch Outlook and verify that your NK2 file is autocompleting for you!

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