Managing cron and similar E-Mails from headless systems

[Chris Green]

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?

-- 
Chris Green