Hi @Sajeer Hajib ,
Welcome to our forum!
What type of account are you using? Is it an POP or IMAP or Exchange account?
Does the issue also exist on the web?
Given this case, you may need to confirm Outlook has been indexed, we may even try rebuilding the Index to check the result.
In Outlook, File > Options > Search > Indexing Options.
Make sure Outlook is included and if you need to rebuild the index, click Advanced > Under Index Settings > Click Rebuild.
If that doesn't help, it is recommended you create a new profile and re-add your account:
Go to Control panel > Mail > Show Profiles > Add, then re-connect your account.
Hope above suggestions may help you.
If you still need help on this, feel free to contact us.
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