In some versions, you can simply click More to continue loading messages from the server .
Click the Include Older Results button at the bottom of your search list to increase the count (usually up to 250) .
In Outlook 2016 and later, the application first submits a query to the Exchange server before rendering results . How to View More Results
This "cap" allows for "lickety split" response times .
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
Microsoft introduced these caps to prevent long wait times while searching large mailboxes.