Hi @Rubiat Rafi
Please first assign the Mailbox Import Export role to the admin account you are using in Exchange Admin Center>permissions>admin Roles.
Then run this cmdlet in Exchange Management Shell to search all mailboxes for this email and export the result to a mailbox you specify (in the following example the search result will be sent to admin's inbox folder):
Get-Mailbox -ResultSize Unlimited | Search-Mailbox -SearchQuery "Subject:Test" -TargetMailbox "admin" -TargetFolder "inbox" -LogOnly -LogLevel Full
Once the search completes, you will receive an email like:
In the csv file you will see results like:
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