From: Greg A. Woods (no email)
Date: Thu Nov 01 2001 - 03:01:14 EST
[ On Thursday, November 1, 2001 at 18:06:41 (+1100), Craig Sanders wrote: ]
> Subject: Re: another interesting spam trick...
>
> the number one best way of blocking spam is to reject mail from
> non-existant domains.
What _exactly_ do you mean there? I suspect you're talking about very
much the same thing as HELO/EHLO validation, except you're skipping the
actual A RR check.
If that's so, and if enough mailers start doing only the initial DNS
lookup and rejecting on HOST_NOT_FOUND then spammers will adapt and
start giving "aol.com", "hotmail.com", "home.com", or some other vastly
popular name that will return some A RR or another. Real validation is
(eventually) necessary to prevent spammers from fraudulently giving an
incorrect (or invalid) HELO/EHLO greeting name.
(checking the domain in the envelope sender address is also necessary of
course, but again that's one the spammers have already adapted somewhat
to as many now just use a popular domain as above)
-- Greg A. Woods +1 416 218-0098 VE3TCP <> <> Planix, Inc. <>; Secrets of the Weird <> - To unsubscribe, send mail to with content (not subject): unsubscribe postfix-users
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