My email has a “bounce” option, which trashes the message and returns a “invalid address” to the sender. This sounds way too easy, so what’s the downside? I’m sure some hacker has had his (her) way with the feature.
Does it work as advertised?
Peace,
mangeorge
Do you plan to do this to spammers, or just people you once had contact with but now wish to cut off? If the former, all you’re doing is clogging up the inbox of the unfortunate host whose server has (probably) been hijacked by the spammer.
The From or Reply To addresses are practically never who actually sent the message, so your bounce messages are effectively spamming some innocent person.
This one is from “National Liverwood Promotions Inc”, from whom I have won “£1,500,000 Great British Pounds” 
Can I clog up their inbox? or is it still some innocent?
I usually just delete these things, but my usually peaceful soul hungers for revenge.
Bouncing emails from spammers will accomplish nothing. Use the bounce feature for actual humans who you want to leave you alone.
I don’t know any of those.
As one can tell from the OP, I didn’t really expect drawing spammer blood to be that easy.
Back to “delete”, I guess. 
Peace,
mangeorge