Lend your shares for shorts at your own risk. Many folks are never repaid if the trade doesn’t work out. The losses to investors are in the billions - it is a dirty little secret of the SEC, as they don’t follow up to put pressure on the loan receiver to pay up.
I'd be very suspicious of the email. The interest rate is way too high and normally you're not even paid interest. You hold them in a margin account and consent to hypothecate your shares. I think Fidelity has a program where you can earn interest on loaned shares but I don't know anyone who's used it.
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