I have never heard of them emailing. Correspondence is always letters. How did they get your email address? I would agree it is a scam.
The IRS does not call taxpayers to advise of unclaimed funds. This is likely a scam. You can contact your state to find out if you have unclaimed funds and the state representative will guide you as to claiming funds owed to you, but the IRS nor the state will ever call you about unclaimed funds.
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