Update! You can now use a registry key to change back to the simple autocomplete list.
An Administrator had a very valid complaint:
My users were happy with the autocomplete feature in Outlook. At least they were before. They aren’t happy with the new "recent people" feature. How can we bring back the old autocomplete list format?
You aren’t alone in your dislike of the new autocomplete list. Yes, it’s nice to see some pictures next to names, but with only 5 names on the list, its limiting and users need to type more of a name out to bring up the autocorrect entry they are looking for. It's also buggy and hard to remove entries from the Other Suggestions section.
I’m happy to say that Microsoft listened. You can now use a registry key to go back to the old-style list of names. Not only is it a simple list, but it displays at least 40 entries in the autocomplete list.
To enable the old-style autocomplete list, add the DisableAutoCompleteUpdate to this key:
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Options DWORD: DisableAutoCompleteUpdate Value: 1
You'll need to restart Outlook after setting the registry key.
If you don't want to edit the registry yourself, I have this ready-to-use registry key.