Microsoft introduced these caps to prevent long wait times while searching large mailboxes.
If you are seeing a specific number like "(68)" in your search header, it indicates that Outlook has found that many matches in your local index or initial server query . Why Results Are Limited
The phrase "Search results for office 2016 (68)" typically refers to the in Outlook 2016 . By default, Office 2016 applications—particularly Outlook—limit search results to a small number of items (often 75 or 250) to optimize performance in cached Exchange mode .
Click the Include Older Results button at the bottom of your search list to increase the count (usually up to 250) .
In some versions, you can simply click More to continue loading messages from the server .