Bug#996433: transmission-daemon: Transmission fails to send mail using exim4

[JT Hundley]

If that's the official way to fix it, I think so. Hopefully this page stays
findable by search engines so that others trying to get Transmission to
send emails through Exim don't have to do all the troubleshooting that I
did :)
I've made this change to my system, thanks for the tip. I'm still learning
systemd.