You may see this issue if you've just installed Outlook with the default settings, after upgrading from an older version like Outlook 2013 to the most recent version of Outlook 2016, or after applying Office updates.
The problem occurs because a default setting for the account limits mail kept locally on the PC to 12 months.
How to Fix This Issue
You can go to Outlook > Backstage (File) tab > Account Settings > Account Settings > click an account > Change button to find the slider that lets you adjust the setting tfrom 12 months to All.
Note that you'll have to restart Outlook before the new setting will take full effect and it may take quite a while for Outlook to download all your messages.
Backstage (File) tab > Account Settings > Account Settings
Screen 2: Click on an account then click the Change button.
Screen 3: Move the slider from "12 months" to "All", then click Next.
Complete the process by clicking Finish button and you will be directed to restart Outlook.
Please be aware that some users with a great deal of mail in a single folder may start to see performance issues in Outlook as a result of making this change. To resolve this problem, organize your archived mail into subfolders with no more than 25,000 emails in each sub-folder.