phsl / new-api

* fix: support SMTP STARTTLS mode and NTLM auth

Add explicit SMTP STARTTLS configuration for 587-style connections and keep SSL/TLS as the implicit TLS mode.

Prefer PLAIN when advertised, keep LOGIN compatibility, and add NTLM as a fallback for Exchange SMTP servers that require it after STARTTLS.

* fix: respect explicit SMTP encryption mode

* fix: preserve SMTP TLS compatibility