Enable SMTPUTF8.

It's probably safe to do so these days. It definitely is for our servers :)

Author: iqe

README.md

@@ -26,8 +26,8 @@ An example config file is provided in `/opt/willi/etc/willi.conf.example`. Copy
 ## Limitations
 
 * If a client specifies multiple `RCPT TO` headers, only the first is used to select an upstream server. It will receive the complete SMTP session, including all other `RCPT TO` headers. If the upstream server does not accept mail for all recipients, it will reject the mail.
+* Upstream servers must support SMTPUTF8, because Willi will always advertise it.
 * If an upstream server does not support/allow XCLIENT from Willi, it only sees the proxy's IP. This can cause trouble with spam-filtering: If the upstream server blocks Willi's IP or greylists it, no client can send any mail to this server via Willi.
-* No support for "advanced" SMTP features like SMTPUTF8. This is because when the client connects, Willi doesn't know yet what upstream server will be used and what features it supports.
 * If upstream server does not support STARTTLS, Willi falls back to plain connection (even if client sent STARTTLS).
 * No support for authentication. This is by design, as Willi is primarily meant to be used for incoming mail.
 

main.go

@@ -77,6 +77,7 @@ func main() {
 	s.WriteTimeout = time.Duration(config.WriteTimeout)
 	s.MaxMessageBytes = int(config.MaxMessageBytes)
 	s.MaxRecipients = config.MaxRecipients
+	s.EnableSMTPUTF8 = true
 	s.AuthDisabled = true
 	s.TLSConfig = tlsConfig