I thought it was legitimate if Stellar made Airdrop. But authenticity also needs to be checked, because there is a lot of fraud now. In the past, I also got Stellar Airdrop, which was enough to create a Stellar account.
It is from blockchain.com site that a nnounced this XLM airdrop and I think it is legit. In addition to this coin telegraph which is my favorite source of cryptocurrency news features it. It is also reported on coindesk.