@wundayatta I use two of my dummy accounts for similar reasons as you and @Aesthetic_Mess. Alerts from websites like LiveJournal, newsletters, coupons, spam-but-not-spam kind of stuff is sent to them. If I want to create an account somewhere I’m not sure I want to stick with, I’ll use one of those accounts, too. I could easily delete those accounts and not care about all the messages being sent down the drain. I rarely log-in to check them. I’m sure I have hundreds of messages I won’t read.
My third dummy account was one I created for a character I created. It’s not technically mine. I would write messages to myself in their voice as an exercise. I haven’t used it in a long time. Since I don’t actively use the e-mail for anything, I count it as another dummy account.