One of my lesser used email accounts is overflowing this morning, filled with very polite messages like:
Hi. This is the qmail-send program at hurricane.mail.adnap.net.au.
I’m afraid I wasn’t able to deliver your message to the following addresses.
This is a permanent error; I’ve given up. Sorry it didn’t work out.
Thanks very much for the notice, but firstname.lastname@example.org isn’t a real “From:” address. If your email system was configured to examine the sending address, you would recognize that this was unlikely to come from my mail server. And if you’d fed the mail message contents into your spam detector, it would almost certainly tell you this was junk (if it didn’t, you need a better spam detector). Bouncing any email you can’t deliver could also tell a malicious program which addresses got through, encouraging them to try A-Z and noting which addresses didn’t bounce.
When you bounce this message, you double the amount of traffic that spam takes on the internet, and you burden yet another innocent email system who has to process and dispose of the message you should have handled. You have become part of the problem. Please be a good internet and email citizen and silently drop email you cannot deliver. Thanks.