[enh] Allow admin to specify an smtp relay

data/hooks/conf_regen/19-postfix

@@ -23,7 +23,17 @@ do_pre_regen() {
 
   # Support different strategy for security configurations
   export compatibility="$(yunohost settings get 'security.postfix.compatibility')"
-
+  
+  # Add possibility to specify a relay
+  # Could be useful with some isp with no 25 port open or more complex setup
+  export relay_host="$(yunohost settings get 'smtp.relay.host')"
+  if [ ! -z "${relay_host}" ]; then
+    export relay_port="$(yunohost settings get 'smtp.relay.port')"
+    export relay_user="$(yunohost settings get 'smtp.relay.user')"
+    relay_password="$(yunohost settings get 'smtp.relay.password')"
+    echo "[${relay_host}]:${relay_port} ${relay_user}:${relay_password}" > /etc/postfix/sasl_passwd
+    postmap /etc/postfix/sasl_passwd
+  fi
   export main_domain
   export domain_list="$YNH_DOMAINS"
   ynh_render_template "main.cf" "${postfix_dir}/main.cf"

data/templates/postfix/main.cf

@@ -72,7 +72,11 @@ alias_maps = hash:/etc/aliases
 alias_database = hash:/etc/aliases
 mydomain = {{ main_domain }}
 mydestination = localhost
+{% if relay_host == "" %}
 relayhost =
+{% else %}
+relayhost = [{{ relay_host }}]:{{ relay_port }}
+{% endif %}
 mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
 mailbox_command = procmail -a "$EXTENSION"
 mailbox_size_limit = 0
@@ -178,3 +182,19 @@ default_destination_rate_delay = 5s
 # So it's easly possible to scan a server to know which email adress is valid
 # and after to send spam
 disable_vrfy_command = yes
+
+{% if relay_user != "" %}
+# Relay email through an other smtp account
+# enable SASL authentication
+smtp_sasl_auth_enable = yes
+# disallow methods that allow anonymous authentication.
+smtp_sasl_security_options = noanonymous
+# where to find sasl_passwd
+smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
+{% if relay_port == "587" %}
+# Enable STARTTLS encryption
+smtp_use_tls = yes
+{% endif %}
+# where to find CA certificates
+smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt
+{% endif %}

src/yunohost/settings.py

@@ -71,6 +71,10 @@ DEFAULTS = OrderedDict([
         "choices": ["intermediate", "modern"]}),
     ("pop3.enabled", {"type": "bool", "default": False}),
     ("smtp.allow_ipv6", {"type": "bool", "default": True}),
+    ("smtp.relay.host", {"type": "string", "default": ""}),
+    ("smtp.relay.port", {"type": "int", "default": 587}),
+    ("smtp.relay.user", {"type": "string", "default": ""}),
+    ("smtp.relay.password", {"type": "string", "default": ""}),
 ])