Applies to: Outlook 2016, Outlook 2019
"No results" is shown when searching for contacts in a shared mailbox in Outlook.
- In Outlook choose File > Options > Search
- Select the results option "Current folder. Current mailbox when searching from the inbox"
- Select OK
Note that this will change the default search scope for email searches as well. This is easy to override on a per-search basis using the drop-down to the right of the email search box.