Revert Outlook 2016 Autocomplete replaced with Recent People.

To Fix this annoying problem go into click on start + run or Windows key + R or click on start and type regedit.

Once in the registry go to 

HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Option 

and right click create new dword and name it DisableAutoCompleteUpdate

then modify it giving it a HEX value of 1 

Restart your outlook.!