This post is related to the popular question "How to change the hostname on Linux?", as exim pulls the hostname from the "official sources" on debian.
and set the short system name there.
which contains the localhost entry and the system name entry, in the form
<IP> <Hostname_FQD version> <Hostname>
compare this here.
For good measure, edit /etc/mailname
to have it contain the FQD name.
Run the start script that anounced the hostname on system start-up to propagate the hostname around:
Test that your system identifies itself as set with hostname -f
If exim is running, restart it to make sure it notices the change
Here, there's no need to re-build the exim configuration with update-exim4.conf, as the hostname is not stated in the exim config files, it's always pulled dynamically.
FQD or FQDN means fully-qualified-domain-name, and is usually in the form host.example.com
When you're done configuring the actual system, make sure that your reverse DNS is configured properly.
Run: $ dig +noall +answer -x <your server's IP address>
This will give you the reverse DNS lookup of your server's IP, or the "PTR record". In my case, the PTR record is set via a system admin panel of my hosting/housing provider. So, go there and make sure it matches what you configured in exim.
More exim4 related posts on goeszen: tag "exim4"