+15. Main option "smtp_backlog_monitor", to set a level above which listen
+ socket backlogs are logged.
+
+16. Main option "hosts_require_helo", requiring HELO or EHLO before MAIL.
+
+17. A main config option "allow_insecure_tainted_data" allows to turn
+
+18. TLS ALPN handling. By default, refuse TLS connections that try to specify
+ a non-smtp (eg. http) use. Options for customising.
+
+19. Support for MacOS (darwin) has been dropped.
+
+