A user came to me with a problem:
I'm using Outlook 2016 on a Windows desktop. Do you know if it's possible to add Contact Groups to the list of Auto-Complete options? It’s only suggesting 'People'. When we email the Contact Group but it doesn't appear in Auto-Complete after that.
Not including local contact groups in the autocomplete list is a bug. Microsoft is aware of it and working on it. Until this is fixed, if you rely on autocomplete, you can roll back to Build 8201.2200 or Build 8431.2107. Note that Groups in the Exchange GAL do show up in autocomplete, only local groups are affected.
If you type just enough of the group name to be unique, Outlook will resolve the name to the contact group when you tab out of the field. If Outlook doesn’t resolve it immediately, you can press Alt+K to force auto-resolve.