There were two possible solutions here:
- Set the
dc_relay_domains
to*
inupdate-exim4.conf.conf
; - Use SMTP authentication to ensure that the sender is allowed to have unrestricted access to the sending capabilities of Exim4.
Going with option 2 is the only way to prevent an open relay and so I did that. I set an SMTP username and password in my mail clients (Outlook 2007, Thunderbird etc.) and uncommented the cram_md5_server
and login_server
authenticator in Exims /etc/exim4/conf.d/auth/30_exim4-config_examples
file. Then updated with dpkg-reconfigure exim4-config
.