I had the same concerns at first, so full disclosure: I do scambaiting in my spare time and use a virtual machine to safely handle and analyze malicious content when working on campaigns (mostly research and reverse engineering).
I ran the email through a virtual instance and confirmed it’s legitimately owned by Square Enix. It passed all verification checks.
Edit: To be clear, it does not ask you for any login credentials etc. I think the survey is linked to your account's email. My Discord group report that some have received it and others haven't. Everyone who has received it is still subscribed to the game, too.
https://imgur.com/a/LgfrEVy
Interestingly, this same email address was brought up on the forums about 12 years ago, and it was confirmed back then that it belongs to SE—specifically their promotions department:
https://forum.square-enix.com/ffxiv/threads/65130
On top of that, several users on both the forums and Reddit have confirmed receiving game codes through that domain. I can confirm this myself as well:
https://imgur.com/a/bH780Bp