I have a very high end user on 365 (16.0) and their client is freezing up every time they try to reply or do a new email. I read up and people are saying this happens when the Nickname file is filled. They suggest cleaning it out but this user wants all their contacts in this file. I do not want to remove anyone so I was going to copy the registry file and increase it. However I can't find this folder. AutoNameCheck does not exist. Any suggestions? I was going to try a fresh install but I doubt it will fix it.
The Autocomplete cache hasn't been a separate file for several Outlook versions now, it's stored inside the mailbox (assuming you are on Exchange). Definitely try a new profile first, also try running Outlook in safe mode (hold the CTRL key while launching it or launch it via "Outlook /safe" in the run box).