This is a base Exim docker image configured to act as a relay with some basic
authenticators are configured, so by default it will
fail delivering all mail.
You can use it as a base for your docker images. Put your configuration
/etc/exim/exim.conf or to the following included files:
relay_from_hosts host list which is used in acl checks.
10.0.0.0/8 : 172.16.0.0/12 : 192.168.0.0/16