How to fix Outlook's annoying "nickname autocomplete' problems

A number of friends have asked me over the years how to reset or disable Outlook's "nickname cache" feature. If you're not sure what this is, it's what happens when you are composing an email message and begin typing a name or email address into one of the address fields in Outlook. Outlook will try to be helpful and suggest a list of names (nicknames) based on a cache of previously entered addresses. The problem with this is that over time the cache gets populated with a litany of old or incorrect addresses, and it can become quite an annoyance if you don't pay attention to what you're doing.

After a bit of research, I stumbled across two solutions to the problem: 1) turn off the feature all together, and 2) reset the cache.

1. Turning off the nickname cache feature
This is much simpler than I thought it would be. First, start Outlook, and then select Tools...Options, followed by Email Options, and then click the Advanced E-Mail Options button (this was tested in Outlook 2003--other versions are likely to be the same, only different ;-) ). In the advanced options dialog, toward the bottom, there is a check box titled 'Suggest names while completing To, CVc, and Bcc fields'. Simply uncheck, click OK, and the "feature" will go away permanently.

2. Resetting the nickname cache
If you happen to *like* the nickname cache/autocomplete feature, but want to clean out all of the junk that's accumulated, you'll need to find the nickname file and delete it. The nickname cache file always has an extension of '.nk2' on the end of it, so finding the file is as simple as searching the hard drive for all files that end in .nk2. I prefer to use the search assistant (hit the Start button, followed by the 'Search' icon...if you're using Windows Desktop search, you'll need to click on 'search assistant' toward the bottom left of the screen). Then select 'All files and
folders', and be sure to click the advanced options and select 'Search System' and 'Search 'Hidden' files. In the file name field, type *.nk2 and then click the 'search' button.

On my machine, the file was named 'Outlook.nk2'. Once it's been found, shut down Outlook, delete or rename the file, and then restart Outlook. Outlook will recreate the file from scratch and begin the process of caching nicknames anew.

References

Microsoft Outlook Auto Complete enable or disable?
How to reset the nickname and the automatic completion caches in Outlook