It looks like both:
and
currently resolve to the same IP address. If so, what is the reason to have both as MX records (one thought is that in the future lisa-relay can be set behind the scenes to a different IP)?
Great question!
You were correct in your assumption, the goal is to reserve the ability to add backup relays later. For the most part backup relays are not a big deal because MTAs have the job of retrying emails that can’t be delivered due to connection failures, which means that downtime generally does not result in lost inbound emails. However, I want room for unusual circumstances or a change in behavior, and this way no one has to make any changes to facilitate movement in that direction.