Configurable OpenSSL versions and ciphers (#387)

config/postal.defaults.yml

@@ -68,6 +68,8 @@ smtp_server:
   tls_enabled: false
   tls_certificate_path: # Defaults to config/smtp.cert
   tls_private_key_path: # Defaults to config/smtp.key
+  tls_ciphers:
+  ssl_version: SSLv23
   proxy_protocol: false
   log_connect: true
   strip_received_headers: false