Internal aliases were served over plain HTTP only — correctly refused a
public certificate (no public CA can validate a private name), and then
left with nothing. The mesh has two authorities for its two name spaces
(08-connectivity §2), so the proxy now takes an optional internal ACME
directory and dispatches at the handshake by the same question HostPolicy
already answers: which authority may certify this name at all.
A route may also say its target speaks https, with insecure for a backend
whose own certificate nothing would trust — the shape Mailu's webmail
front needs, and the exception: everything else the mesh hands this proxy
stays plain http on the private network.