From my understanding without this option you are allowing "legitimate" advertising companies to send advertisements since your server doesn't instruct otherwise. I was thinking of it as a snail mailbox sticker stating:`No ads please` :) .
– pl1nkJun 05 '13 at 18:00
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Originally the idea was that having a notice in place would make it possible to sue spammers - in effect an attempt at a technological solution to a social problem. It has not worked.
– Jenny DJun 07 '13 at 07:04
It may actually provide feedback to spammers so they can fix their emails to bypass spamfilters. It's the "evil bit" on steroids. This RFC3865 should be deprecated.
– MartijnSep 09 '16 at 10:50