fatal critical
Final or not
Whether this outcome ends the message or leaves it to be retried.
In detail
The engine's own verdict on permanence, which is more reliable than inferring it from the code — a 4xx is usually temporary and sometimes not, and the engine has already applied its rules. For Hub this is the field that should drive the hard/soft distinction on MailerQ nodes, rather than re-deriving it from codes as we do for PowerMTA.