This is kind of an embarrassing problem, because I should know how to fix it myself, but I don't.
I recently set up exim4 on a development server I have running Ubuntu. I set it up to send mail using gmail's smtp so that I could test some of the mail functions of a project I was working on.
Now I'm getting mail delivery errors in my gmail account daily, saying that messages were not delivered to root@(username).com and www-data@(username).com
I can't remember where the settings would be to change these addresses so it doesn't try to send to them anymore. I've checked in /etc/aliases, but it wasn't there.
There are two folders - root and www-data - in my /var/mail directory. If I delete those, will that fix the problem?