Any Member or Catalyst is entitled to an @enspiral address.
They pay an additional annual fee to the foundation which is set by the board. See the current cost at the Email accounts guide​
Any Contributor with an active subscription (full or subsidized) can keep their email address regardless of how / when they received it.
Catalysts can decide exceptions to the rule
This agreement was formed through the Assembly Sprint | April 2019 via this Loomio thread​