Fix settings, improve docs, add `networks` for Drone

.drone.yml

@@ -10,6 +10,9 @@ steps:
       purge: true
       deploy_key:
         from_secret: drone_ssh_swarm_test
+      networks:
+        - mail
+        - proxy
     environment:
       DOMAIN: swarm-test.autonomic.zone
       STACK_NAME: postfix-relay

README.md

@@ -7,17 +7,22 @@ The basic idea is to run one instance of this on each swarm, and configure that
 swarm's apps to send all their email through it.
 
 By default, this stack will try to deliver e-mail directly (i.e. looking up the
-recipient's mail server using `MX` records). For this to work, you will need to
-set up reverse DNS and SPF.
+recipient's mail server using `MX` records). 
+
+**NOTE**: If you use this direct delivery, make sure that:
+ - your Traefik server and host firewall are configured to allow port 587, 
+ - you have an MX record for your configured `$DOMAIN` pointing to this server,
+ - you have an SPF record for `$DOMAIN` that includes `mx` or this server's IP
+ - you have a reverse DNS (rDNS / PTR) record for this IP that matches `$DOMAIN`
+
+(These requirements mean that you can only deploy one direct-delivery instance
+of this app per swarm host..)
 
 Alternatively, you can easily route mail through a smarthost / relay host like
 Mailgun or Gandi -- see [`RELAYHOST` and related parameters][boky-postfix-options].
 
 FIXME 3wc: Pass `RELAYHOST` etc. from `.envrc` to service
 
-TODO 3wc: Can you run more than one instance of this on a swarm? How could we handle
-that in terms of reverse DNS?
-
 ## Basic usage
 
 1. Set up Docker Swarm and [`abra`]
@@ -25,7 +30,8 @@ that in terms of reverse DNS?
 3. `git clone https://git.autonomic.zone/compose-stacks/postfix-relay.git && cd postfix-relay`
 3. `cp .envrc.sample .envrc`
 4. Edit `.envrc` - be sure to change `DOMAIN` to something that resolves to
-   your Docker swarm box
+   your Docker swarm box, and add any extra domains (including subdomains) you'd
+   like to be able to send mail from in `EXTRA_SENDER_DOMAINS`.
 5. `direnv allow` (or `. .envrc`)
 6. `abra deploy`
 

compose.yml

@@ -16,10 +16,9 @@ services:
     environment:
       FORCE_COLOR: "1"
       TZ: ${TZ}
-      INBOUND_DEBUGGING: "${INBOUND_DEBUGGING:-0}"
-      ALLOWED_SENDER_DOMAINS: "${EXTRA_SENDER_DOMAINS} ${DOMAIN}"
-      POSTFIX_myhostname: "${DOMAIN}"
-      MASQUERADED_DOMAINS: "${MASQUERADED_DOMAINS}"
+      INBOUND_DEBUGGING: ${INBOUND_DEBUGGING}
+      ALLOWED_SENDER_DOMAINS: ${DOMAIN} ${EXTRA_SENDER_DOMAINS}
+      POSTFIX_myhostname: ${DOMAIN}
     deploy:
       restart_policy:
         condition: on-failure