+# This transport is used for delivering messages to a smarthost, if the
+# smarthost router is enabled. This starts from the same basis as
+# "remote_smtp" but then turns on various security options, because
+# we assume that if you're told "use smarthost.example.org as the smarthost"
+# then there will be TLS available, with a verifiable certificate for that
+# hostname, using decent TLS.
+
+smarthost_smtp:
+ driver = smtp
+ message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
+ multi_domain
+ #
+.ifdef _HAVE_TLS
+ # Comment out any of these which you have to, then file a Support
+ # request with your smarthost provider to get things fixed:
+ hosts_require_tls = *
+ tls_sni = $host
+ tls_verify_hosts = *
+ # As long as tls_verify_hosts is enabled, this won't matter, but if you
+ # have to comment it out then this will at least log whether you succeed
+ # or not:
+ tls_try_verify_hosts = *
+ #
+.ifdef _HAVE_OPENSSL
+ tls_require_ciphers = HIGH:@STRENGTH
+.endif
+.ifdef _HAVE_GNUTLS
+ tls_require_ciphers = NONE:+VERS-TLS1.2:SECURE192
+.endif
+.endif
+
+