Proof for sent email confirmation after purchase

Hello, is there a way to check the emails that were sent as a confirmation for the purchase. We have a customer claiming that she didn’t receive the confirmation email and thus she wants a refund because the period of 14 days in which we give refund is still lasting. She downloaded the videos that we sell and now wants a refund but we need a proof that the email was sent to her.

Is there any log where this information is stored?

To be clear, I am talking about the email confirmation which a customer receives right after finishing the purchase.

Thank you

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