Outlook 2010 autocomplete resets after closing Outlook

What:

Outlook 2010 on Windows 7

Problem:

Outlook only keeps autocomplete list for current session, when closed and reopen autocomplete list is empty.

Solution:

Navigate to C:\Users\<username>\AppData\Local\Microsoft\Outlook\RoamCache
Rename file Stream_Autocomplete_some_random_characters.dat
In Outlook select File > Options > Mail, scroll down click Empty Auto-Complete List.

Now your list should build up, if you have an autocomplete file backup, close Outlook and copy it to above location, rename file.