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To better resolve this issue, please provide more details:
What is your email account type (POP/IMAP/Exchange)?
What version of your Outlook is? Please make sure to update to the latest version.
Can emails be searched from the top search box? If you find a search, hover over the search results to display the directory where the email is stored.
There are many reasons for this problem. Try the following possible solutions to troubleshoot:
Try resetting the folder view. Press the Win+R keys to open the Run dialog box. Then, type outlook.exe /cleanviews and click the OK button.
If that doesn't work, please try to create a new profile in the Outlook client to check if there are any differences.
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