require TLS on SMTP submission (port 587) to prevent accidental client...

require TLS on SMTP submission (port 587) to prevent accidental client misconfiguration, although this has no other practical consequences since without TLS clients couldn't authenticate anyway

setup/mail-postfix.sh

@@ -65,6 +65,8 @@ tools/editconf.py /etc/postfix/main.cf \
 # * Do not add the OpenDMAC Authentication-Results header. That should only be added
 #   on incoming mail. Omit the OpenDMARC milter by re-setting smtpd_milters to the
 #   OpenDKIM milter only. See dkim.sh.
+# * Even though we dont allow auth over non-TLS connections (smtpd_tls_auth_only below, and without auth the client cant
+#   send outbound mail), don't allow non-TLS mail submission on this port anyway to prevent accidental misconfiguration.
 # * Require the best ciphers for incoming connections per http://baldric.net/2013/12/07/tls-ciphers-in-postfix-and-dovecot/.
 #   By putting this setting here we leave opportunistic TLS on incoming mail at default cipher settings (any cipher is better than none).
 # * Give it a different name in syslog to distinguish it from the port 25 smtpd server.
@@ -75,6 +77,7 @@ tools/editconf.py /etc/postfix/master.cf -s -w \
 	"submission=inet n       -       -       -       -       smtpd
 	  -o syslog_name=postfix/submission
 	  -o smtpd_milters=inet:127.0.0.1:8891
+	  -o smtpd_tls_security_level=encrypt
 	  -o smtpd_tls_ciphers=high -o smtpd_tls_exclude_ciphers=aNULL,DES,3DES,MD5,DES+MD5,RC4 -o smtpd_tls_protocols=!SSLv2,!SSLv3
 	  -o cleanup_service_name=authclean" \
 	"authclean=unix  n       -       -       -       0       cleanup