I don't think I need exim4 -- how do I get rid of it? [SOLVED]

[durhammer]

I don't like having extra baggage in my RAM, such as "ModemManager" (don't have a modem!) and exim4 (don't use my laptop as an email server or forwarding service). I disabled ModemManager, but exim4 gets a permissions error when I try to disable it. (Oh duh -- do I need to do sudo systemctl ... ?  OK, nope. Besides, I got prompted for password the first time.)

Why is this so difficult to do?

UPDATE: So apparently, doing the systemctl set things in motion to clobber the service, but only after a reboot, which I just did and the thing's gone. DONE!