I've also read that data is read from this hidden mailbox 'thing' on Outlook startup, into the local AppData 'Stream_Autocomplete_blahblahblah.dat' file, and that as Idea which, nor how or even if it is possible to examine it. I've read that this 'thing' is either a hidden file, a hidden folder or a hidden message. nk2 files, but rather stores the data in some hidden 'thing' in the user's mailbox on the server. I understand that Outlook 2010 no longer uses. And naturally, he really likes this featureĪnd we look really stupid for not being able to get it working for him again. He is a standard domain user on a Windows 2008R2 domain, and we are running Exchange 2010 SP1. My problem is simply that, for a certain user (who of course happens to be the executive director), Outlook 2010 no longer retains address autocomplete information. None of the answers I've found have brought much clarity to the issue. I know that this has been asked before and I apologize in advance for opening up the topic again.