For some reason when using Outlook, all of the saved names/email addresses in the Outlook cache (.nk2) file was not being read by Outlook 2010. When looking at the .nk2 file in userAppDataRoamingMicrosoftOutlook it had been renamed to Outlook.nk2.old. When I renamed the .nk2 file back to Outlook.nk2 file, Outlook still would not use the autocomplete file. When having no .nk2 file Outlook didn’t create a .nk2 file either….weird. So, I found a way to import the .nk2 file in outlook: Close Outlook, go to the run window and type outlook.exe /importnk2
Microsoft Support KB – link