Did upgrading from outlook 2010 to 2013 mess up your auto complete list?
Well this is what worked for me… I noticed that 2013 created a new “Stream_Autocomplete.dat” file (This file will be located here: C:\Users\YOUR-USER-NAME\AppData\Local\Microsoft\Outlook\RoamCache)
So what I did was I copied the entire file name and then renamed my previous largest (from 2010) “Stream_Autocomplete.dat” file to the new one that 2013 created.
Once the entire file name is copied, delete the “2013” .DAT file, or just MOVE it to a different location.
Once that is done, start Outlook and bang! You should have your auto complete list from your Outlook 2010