david.brinegar at acm.org
Mon Feb 16 09:53:40 PST 2004
Paul A. Hoadley wrote:
> Let's imagine that Charles gets a bounce notification, but it doesn't
> reach his threshold for doing anything more about it. Bob loses
> legitimate mail.
Bounce messages are typically not good enough to avoid this. The
other day a client tried to send an e-mail that exceeded my ISP's
limit and was told something like "mailbox is full" and had no idea
that the mailbox was empty but for their gigantic message. Thank
you qmail. Funny enough, they just assumed it was another of those
DNS blocks and had nothing to do with my mailbox, so I suppose
they've grown weary of these DNS blocked messages.
Another example is prodigy.net, which is spread out all over AOL and
SBC DSL and who knows what else. When you send a message as a DSL
customer, it goes out of a random mailer on prodigy.net including
some that are DNS blocked by computers using the same network. So
when you send mail to other prodigy.net users, you randomly get DNS
blocked. The error message says that some.prodigy.net rejected a
message from another.prodigy.net, which is mystifying to say the
So it is definitely over-used and misused. But I must admit that
limited DNS blocking is great. Like blocking dial-up users who send
directly instead of out the ISP's smtp server. Spammers are sending
a lot of traffic from cracked dial-up computers, and this method
chops that off cleanly. The trick is to make sure that the
rejection message is helpful to someone who might bother to read it.
A bunch of numbers and "hello my name is qmail" doesn't cut it.
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