Literal LOGIN prompt matching rejected valid credentials and substring AUTH
selection could choose an unadvertised mechanism. Use exchange order and
complete mechanism names, preserve server reply classes, and classify
unsupported mechanism lists as configuration failures.
Share the implicit TLS decision between connection tests and delivery so a
port-465 test does not attempt STARTTLS inside an established TLS session.
Add real SMTP controls and persisted queue verdict verification.
rcourtman
960b5771ec