[CentOS] Postfix, system notifications and local servers

Mon Jun 25 09:29:33 UTC 2018
Tony Mountifield <tony at softins.co.uk>

In article <7919547a-2a23-901f-607e-5aef7300f52a at microlinux.fr>,
Nicolas Kovacs <info at microlinux.fr> wrote:
> Hi,
> I have CentOS 7 running on half a dozen public servers. For some stuff
> like automatic updates using yum-cron, I have Postfix installed with a
> relatively basic configuration. This allows me to send important
> notifications to my mail address info at microlinux.fr. When there's a
> batch of updates, I get one mail per machine, so I can check quickly if
> everything went OK without having to connect to the server.
> Now I'd also like to use this setup on machines that aren't in a
> datacenter and facing the Internet. For example, servers that have
> "dummy" hostnames like nestor.microlinux.lan or sauvegarde.scholae.lan.
> Is there a way I can setup Postfix so this machine can send an e-mail to
> info at microlinux.fr, even if 'hostname --fqdn' returns a "dummy" hostname?

When you say "[not] facing the Internet", do those machines actually have
access to any other machines that ARE facing the internet? If not, then
you have to think "what possible route could an email take from the machine
to the email server for microlinux.fr?"

If they do have access to an internet-connected machine, then you could
set up postfix on the source machines to relay all emails via a suitable
SMTP mail relay. You do this by setting the "relayhost" option in the
config file /etc/postfix/main.cf. There are plenty of examples available
via Google.

You also need to think "What happens if an email from nestor.microlinux.lan
bounces for some reason? Where would the bounce go? If the sender address
is indeed in the .lan domain, the bounce would be undeliverable, so you
might want to investigate sender address masquerading.

Tony Mountifield
Work: tony at softins.co.uk - http://www.softins.co.uk
Play: tony at mountifield.org - http://tony.mountifield.org