spacecowboy/postfix repository overview

⁠spacecowboy/postfix

Postfix is the SMTP server, delivering outgoing mail and accepting incoming mail (after verification).

docker run --rm --name=postfix \
  --net=mail_network \
  --hostname=mail.example.com \
  -e myhostname=mail.example.com \
  -e mydomain=example.com \
  -p 25:25 \
  -p 587:587 \
  -v /root/opendkim-keys:/etc/opendkim/keys \
  -v /etc/letsencrypt/live/example.com/privkey.pem:/etc/ssl/private/ssl-cert-snakeoil.key \
  -v /etc/letsencrypt/live/example.com/fullchain.pem:/etc/ssl/certs/ssl-cert-snakeoil.pem \
  -t spacecowboy/postfix

The hostname must be specified with --hostname and also as -e myhostname, and the domain as -e mydomain.

Port 25 must be exposed if you want to receive mail from the internet. It only handles incoming email and will reject any emails which are not addressed to a known user. Emails which are addressed to a known user are then handed off to spam filtering. Port 587 handles outgoing e-mail and requires a connection with TLS and a user/password login. Since only authorized users can send e-mail to the internet, these are not subjected to spam filtering but instead they are signed with DKIM.

The first volume to specify is where to save the DKIM-keys. You should change /root/opendkim-keys to a suitable location on your machine. This allows the same key to be reused, which we want since you should publish the public key in your DNS records. On startup the container will print what the DNS record should contain.

The other volumes are to override the default certificate with your own valid one to get proper TLS support without warnings. If you really don't want to have proper certificate (for testing for example), you can just omit those volumes and use the default self-signed one.