It seems upstream has some problems with RWX volumes in longhorn 1.5.3
where share-mananger status isn't properly assessed and as a result not
restarted when single share-managers go down. The fix for now is to
manually patch the share-manager objects with an error state, which
triggers longhorn to repair itself.

In order to notice that, this alert triggers and allows to manually fix
the problem until a new upstream release is ready, that fixes the
problem.

References:
https://github.com/longhorn/longhorn/issues/7183#issuecomment-1823715359
https://github.com/longhorn/longhorn/wiki/Release-Known-Issues

This patch configures postfix to reject incoming email from its own
domains this is an effort to fight phishing of emails from my own domain
claiming to be from postmaster or alike.

References:
https://superuser.com/questions/964958/make-postfix-reject-incoming-email-spoofed-as-from-my-own-domain