#+TITLE: Lemmy

** Configure SPF and DKIM for SMTP postfix-relay

Source: [[https://github.com/wader/postfix-relay#spf]]

- Add remote forwarding for rsyslog.
- Make the DKIM keys persist indefinitely in a volume at ~./volumes/postfix-dkim:/etc/opendkim/keys~.
- ~./volumes~ is relative to the parent directory of the ~docker-compose.yml~ file for the Lemmy instance. E.g. ~/docker/lemmy/volumes~.

Edit ~docker-compose.yml~:

#+BEGIN_SRC yaml
postfix:
  image: mwader/postfix-relay
  environment:
    - POSTFIX_myhostname=lemmy.hyperreal.coffee
    - OPENDKIM_DOMAINS=lemmy.hyperreal.coffee
    - RSYSLOG_TO_FILE=yes
    - RSYSLOG_TIMESTAMP=yes
    - RSYSLOG_REMOTE_HOST=<ip addr of remote logging server>
    - RSYSLOG_REMOTE_PORT=514
    - RSYSLOG_REMOTE_TEMPLATE=RSYSLOG_ForwardFormat
  volumes:
    - ./volumes/postfix-dkim:/etc/opendkim/keys
    - ./volumes/logs:/var/log
  restart: "always"
  logging: *default-logging
#+END_SRC

#+BEGIN_SRC shell
docker-compose up -d
#+END_SRC

On domain registrar, add the following TXT records:

| Type | Name                  | Content                                      |
|------+-----------------------+----------------------------------------------|
| TXT  | lemmy                 | "v=spf1 a max ipv4:<ip addr of server> -all" |
| TXT  | mail._domainkey.lemmy | "v=DKIM1; h=sha256; k=rsa; p=<pubkey>"       |

The content of ~mail._domainkey.lemmy~ is obtained from the log output of the wader/postfix-relay Docker container.

#+BEGIN_SRC shell
docker logs lemmy-postfix-1
#+END_SRC

To test this, allow a few hours for the DNS changes to propagate, then log out of the Lemmy instance and send a password reset request. If the reset confirmation email doesn't go to the spam folder, it works. The email service provider will be able to determine the email is from an authentic email address.

*** Resources
- [[https://en.wikipedia.org/wiki/DomainKeys_Identified_Mail][DomainKeys Identified Mail - Wikipedia]]
- [[https://en.wikipedia.org/wiki/Sender_Policy_Framework][Sender Policy Framework - Wikipedia]]
- [[https://en.wikipedia.org/wiki/DMARC][DMARC]]