From: "Bruce Brown" <bruce(_dot_)brown(_at_)openwave(_dot_)com>
...
Other spammers know that their target lists tend to fill with garbage
as addresses are abandoned and as target address harvesting mechanisms
get confused (e.g. by message-IDs). They know that some major ISPs
by rumor including AOL automatically blacklist STMP clients by IP
address after too many bad target addresses. This provides a strong
incentive for spammers to clean their target lists. To do that, they
need drop-boxes get delivery failure notifications.
This seems to argue that there should be no feedback to spammer to
allow them easy means to clean their lists, since bad RcptTo may
trigger spammer detection.
Those of us (and there are many) who use "traps" try to keep them
popular among spammers. We never report spam received by our traps,
because we cannot know whether the address of the trap is hidden in
a Message-ID or Received queue-ID, hidden in the pattern of blanks,
capitalization, and punctuation in the body, or could be guessed by
checking IP addresses and dates in sender logs.
On the other hand, it is even more important that every false positive
generate an SMTP error response or a "bounce." Every spam defense
used on mailboxes intended to receive mail from strangers has some
false positives, if you define "false positive" broadly.
Vernon Schryver vjs(_at_)rhyolite(_dot_)com
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