On Sep 19, 2007, at 2:35 PM, Martin Zobel-Helas wrote:
Hi,
On Wed Sep 19, 2007 at 14:09:32 -0700, David Brodbeck wrote:
That's true, although the sending server will generate a bounce back
to the sender. So the mail doesn't disappear down a black hole, at
least.
Great! with million senders being forged every day that helps a lot.
Pretty much all the spam I see these days is sent direct-to-MX by
trojaned PCs running dedicated spam-spewing software. Rejecting at
SMTP time doesn't create any backscatter spam in this situation,
because the spamware isn't going to bother to generate a bounce!
Accepting a message and *then* bouncing it would indeed generate
backscatter spam and would be the wrong way to go about it, of
course. Once the SMTP transaction is over a message should never be
bounced, but it's OK to refuse to accept it at SMTP time, IMHO.
Older Exchange servers can be a major culprit in backscatter spam. I
discovered a while back that Exchange 5.5 accepts *anything* at SMTP
time, even invalid usernames, then creates a bounce message later.
This is utterly broken. Some Linux MTAs can be configured this way,
too, and misguided folks sometimes implement spam filtering this way.
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