[ On Thu, January 22, 1998 at 10:51:33 (-0700), Sherwood Botsford wrote: ]
> Subject: [EXIM] They keep knocking when nobody is home!
>
> A while ago I added ix.netcom.com and worldnet.att.net to my
> reject list. Neither one takes 'no' for an answer.
>
> I suspect that they are assuming that they are being rejected
> because the system is busy.
That's not necessarily so. Each bounce could in fact be from a separate
spam message directed at your server.
However it is true that some mailers will not take 'no' for an answer --
i.e. they treat a 500 series error in some circumstances the same as a
400 error. I've been told that Netscape's mail server is one that
either did or does this, or can be configured to do this. During the
incedent where I learned this I also learned that the remote site's
admin had reduced the retry time for my site to less than a minute under
the mistaken belief that something must be wrong at my end. Some people
cannot read and should not be allowed anywhere near a computer, esp. not
with the root password.
In other cases I've seen abused mailers knocking on my door every five
minutes or so -- as quickly as they could get throuh their queues to the
next message destined to my site.
Typically sendmail, and probably a few others, will ignore any error
from HELO and proceed on to the RCPT TO: and only bounce the message
when they get a 500 then. (The Netscape mailer was doing the same, but
didn't give up.) They do this because sendmail itself will sometimes
issue errors for HELO, but if you persist and give a RCPT TO: they'll
still accept the message, sticking to the very letter of RFC-1123's
asinine "Robustness Principle".
--
Greg A. Woods
+1 416 443-1734 VE3TCP <gwoods@???> <robohack!woods>
Planix, Inc. <woods@???>; Secrets of the Weird <woods@???>
--
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