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Last pushed: 10 months ago
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Postfix SMTP relay docker image. Useful for sending email without using an
external SMTP server.


docker pull mwader/postfix-relay or clone and build it yourself. Default
postfix is configured to be an open relay that rely on docker networking
for firewalling. So be careful not to expose it publicly.

All postfix configuration options can be set using POSTFIX_<name> environment
variables. See Dockerfile for default configuration. It will
work without making any changes but you might want to set
POSTFIX_myhostname, the FQDN used by 220/HELO.

Using docker run

docker run \
    -e POSTFIX_HOSTNAME=smtp.domain.tld \
    --name smtp \

Now run some other container with a link to smtp and use it as SMTP server.

Using docker-compose

    - smtp
  # use hostname "smtp" as SMTP server

  image: ox1de/postfix-relay
  restart: always
    - POSTFIX_HOSTNAME=smtp.domain.tld


When sending email using your own SMTP server it is probably a very good idea
to setup SPF for the
domain your sending mail from.


To enable DKIM
specifying a white space separated list of domains using OPENDKIM_DOMAINS.
At container start new key pairs for each domain will be generated if not found
in /etc/opendkim/keys/<domain>". To persist the keys make sure to add a host
directory volume for /etc/opendkim/keys. If your using docker-compose it will
automatically take care of moving data volumes between container recreates.

DNS records to configure can be found in the container log or by running
docker exec -ti <container> sh -c "cat /etc/opendkim/keys/*/mail.txt".


postfix-relay is licensed under the MIT license. See LICENSE for the
full license text.

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