Commit 40a311b0 authored by Phillip Smith (fukawi2)'s avatar Phillip Smith (fukawi2)
Browse files

expand documentation of smtp architecture

parent cf5af803
......@@ -80,6 +80,10 @@ state server is assumed to just exist so in an unlikely case where we have to
entirely redo this infrastructure, the state server would have to be manually
set up.
#### SMTP Configuration
All hosts should be relaying email through our primary mx host (currently 'orion'). See docs/email.txt for full details.
#### Note about opendkim
The opendkim DNS data has to be added to DNS manually. The roles verifies that the DNS is correct before starting opendkim.
......@@ -15,3 +15,32 @@ appropriate category and run `postmap /etc/postfix/users`.
If the user wants to forward email, either enter the destination directly in
the /etc/postfix/users file or enter a username and then put the destination
into `~username/.forward` so that they can edit it themselves.
# SMTP Architecture
All hosts should be relaying outbound SMTP traffic via our primary MX server
(currently 'orion'). Each hosts authenticates using SASL over a TLS connection
to the server. This gives us several benefits:
1. DKIM signing can be done centrally.
2. SPF records require less maintenance as servers are added/removed.
3. Our email reputation is focused on one well-maintained and (hopefully) well
maintained host, rather than distributed across all hosts in our fleet.
4. Central traceability for debugging.
5. Central maintainability for rate-limiting to prevent abuse.
When a new host is provisioned:
- The *postfix* role has a task delegated to 'orion' to create a local user
on 'orion' that is used for the new server to authenticate against. The user
name is the shortname of the new servers hostname (ie, ""
will authenticate with the username "foobar")
- You will need to run the *postfwd* role against orion to update the
rate-limiting it performs (servers are given higher rate-limits than normal
users - see `/etc/postfwd/` for exact limits). This *should*
happen automatically as the *postfwd* role is a dependency of the *postfix*
role (using `delegate_to` to run it against 'orion' regardless of the target
host that the postfix role is being run on)
- Any services on the new host that need to relay mail should relay using SMTP
to `localhost` on port 10027 which bypasses any filtering/restrictions that
are applied by postfix to port 25 traffic.
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