The file is “Stream_Autocomplete_******” where the stars are a long unique identifier. Locate the autocomplete file – \\users\username\appdata\local\microsoft\outlook\roamcache (For use with 2010+ version to another 2010+ version) Those will now show up under the AutoFill.
services related to newer versions of Microsoft Office, please refer to the guide below. old file name extension on the first Start of Outlook 2013. nk2 file, the contents of the file will merge into the existing nickname cache stored in your mailbox.