At the start of this year, I set out to tame, substantially, my email. I was tired of getting dozens of promotional emails a day (and, admittedly, the little dopamine hit from checking email even though I didn't care about the mail was getting old), so I set out to resolve this - and began unsubscribing from everything I didn't care about, or marking as spam (at this point, anything getting into my inbox seems to have a working unsubscribe link - thanks, Google Apps!).
Then, as that torrent subsided, I set about finding more stuff to get rid of. Recently, I've changed around my eBay notifications so I don't get email for "ordered, shipped, delivered." Just one. Thanks, I can check if I care to, but I don't actually care about it being delivered, because I'll find that out when I go check the mail. And I've trimmed back Facebook notifications, though FFS, they make it hard...
About 2 months ago, I started attacking paper junk mail as well. I get a lot of charity contribution requests for some reason, and I've started sending them back with "Thanks, but please take me off your list..." type messages. If they send something nice, I'll toss in a few dollars (like, paper ones), but still tell them to remove me - and, so far, this seems to actually work. Surprisingly. Most of the financial junk mail I get is of the "Enter this URL to be instantly approved!" variety, but the stuff with a prepaid return envelope? I send them their entire mailing material back, and usually tape a few coins to the paper for both added weight and greater annoyance, along with a request to stop sending me junk.
It seems like it's not the type of thing that should work, but, wow. I'm getting a lot less junk mail in my mailbox now! Try it, if you happen to be bored and want to do your little part to help both improve your sanity and reduce the amount of pointless tree killing going on!