Some actual data presented anecdotally
Posted Jul 9, 2011 19:50 UTC (Sat) by anselm
In reply to: Some actual data presented anecdotally
Parent article: A decline in email spam?
It's really a lot better to reject spam during the SMTP dialog rather than after having accepted the message. Once you have accepted the message and decided it's spam, you can't bounce it back to the purported sender since the sender address is likely to be forged. So you write it into the recipient's »spam« folder, which they usually never check, and the message is practically lost.
On the other hand, if you reject spam while the SMTP message is ongoing, the actual sender sees an SMTP error, so if the mail is really legitimate, at least they know that their message can't be delivered. Since, with spam, a large proportion of false positives results from misconfigured DNS at the sender's and things like that, this puts pressure on the senders to fix their systems. You can also try to annoy apparent spammers by »tarpitting«, i.e., putting in deliberate long delays before rejecting their messages, so their servers can't send as much spam out as they would if everyone just accepted it.
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