I have several headless systems doing useful work around the place:-
A Raspberry Pi providing local DNS and DHCP
A Beaglebone Black on our boat monitoring temperatures and batteries
An old desktop doing backups in the garage
etc.
Most of these have one or more cron jobs running periodic rsync backups, copying data, etc. If the cron job has an error then it sends E-Mail to the owner of the job ('chris' in most cases, might be root in a couple).
It's (moderately) easy to set up an MTA and /etc/aliases so that the messages are sent to my normal E-Mail. However I can't come up with a straightforward way of indicating where the messsage is *from*.
You can't just invent a domain name for the headless system because that gets the E-Mail rejected by intermediate systems that try and look up the sender host name. Cron doesn't seem to have any mechanism for setting the sender's name, cron errors just come from 'root@'.
Can anyone suggest a neat way of handling this so that I know where the errors are coming from?