DOMAIN = example.com
HOST = mail.example.com

$ cat {private-key-file-path} > certs/private-key.pem
$ cat {cert-file-path} > certs/cert.pem

$ sudo docker compose up -d

$ sudo docker exec -it mail bash
$ cat /etc/opendkim/keys/{domain}/mail.txt

$ sudo docker exec -it mail bash
$ adduser {username}
$ echo "{username}@{domain}    {username}" >> /etc/postfix/sender_login
$ postmap /etc/postfix/sender_login

sudo docker compose logs -f