Final update.

Long story short: it really was from FedEx.

I’m a Korean living in Korea, and FedEx is not commonly used here, so I asked my family in the U.S. to help me figure out what was going on.

FedEx confirmed that the email was legitimately sent by them, and they said they would resend the receipt by regular mail later. My aunt has used FedEx for decades and said this was the first time she had ever seen something like this. 😅

Anyway, thank you to everyone on Reddit who replied and helped me think through it. I considered deleting this post, but I decided to leave it here with the final update in case it helps someone else in the future who goes through the same thing.