FYI, I received this email from my .au domain registrar (not AWS) a week ago:

Hey, just a quick update on your .au domain(s). Our backend provider for .au is changing their backend provider, and they'll be sending two emails explaining the move (as required by the .au registry): one on December 20th and the followup on January 18th. To be clear, absolutely nothing will be changing to your account, and you don't have to do anything with the emails... they're purely informational. We're just preemptively letting you know so you won't be alarmed.

And yesterday received an email from Hexonet like the one quoted by OP.