Usage

1. Install to /etc/systemd/system:

   • send-mail@.service: systemd unit
   • send-mail: Script invoked by send-mail@.service to send an e-mail

2. Optionally configure recipient's and sender's e-mail addresses in send-mail:

   RECIPIENT=jdoe@example.com
   SENDER=jschmoe@example.com
   

   These default to root@<hostname> and <failed-unit-user>@<hostname>.

3. Add to the unit(s) of whose failures you would like to be notified:

   [Unit]
   ...
   OnFailure=send-mail@%N.service
   ...
   

4. Reload the modified unit(s):

   $ sudo systemctl daemon-reload