On Wed, 2004-09-15 at 00:29 -0700, Tor Slettnes wrote:
> Thanks to those of you who contributed feedback and other input to my
> "Spam Filtering for Mail Exchangers" HOWTO. It is now officially
> published via The Linux Documentation Project:
>
> http://www.tldp.org/HOWTO/Spam-Filtering-for-MX/
A generally excellent reference document -- thanks.
However, in §2.3.3.4 you state that 'Legitimate Delivery Status
Notifications should be sent to only one recipient address" and
encourage the reader to drop the connection if that happens.
Your advice contradicts §2.6.1 of RFC2505, which says that you MUST NOT
(their caps) reject the mail in that case:
The most common case of such legitimate "MAIL From: <>" is to one
recipient, i.e. an error message returned to one single individual.
Since spammers have used "MAIL From: <>" to send to many recipients,
it is tempting to either reject such mail completely or to reject all
but the first recipient. However, there are legitimate causes for an
error mail to go to multiple recipients, e.g. a list with several
list owners, all located at the same remote site, and thus the MTA
MUST NOT refuse "MAIL From: <>" even in this case.
--
dwmw2
