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Re: Mailing list readership (was: Re: lynx-dev How to Lynx)


From: Duncan Simpson
Subject: Re: Mailing list readership (was: Re: lynx-dev How to Lynx)
Date: Wed, 10 Apr 2002 22:07:43 +0100

> > 
> > x.  the precedence header.  it has been in use for decades now.  it was
> >     designed to be meaningful in the context of UUCP, where it
> > differentiated between urgent and not-so-urgent items.  given a certain
> 
> It's more subtle than that, and comes from military messaging.  I think it
> is more to do with what you are allowed to discard under overload.
>

The Precedence: header also affects sendmail's choice of how quickly a message
is sent. The major use has probably shifted to telling clueful autoresponders
not to respond (if the Precedence: is list, bulk or junk respoinding is the
wrong thing---and any software that does not know this should be fixed).

I could check but I think you will find the Precedence: header dicumented in
RFC 822. FYI the precence header does *NOT* have any affect on whether you are
allowed to discard the message, it only allows you to deliver it more slowly,
and perhaps more cheaply as a result (particularly in the days of when almost 
all
mail travelled by UUCP).

<stuff snipped>
 
> As I said before, automatic rejectors should never use header addresses.
> The envelope address is the only safe one to use, although even that 
> will get you removed from lists if you auto-respond to list postings.

<all the rest sniped>

I do not like to shatter to many illusions but both the envelope address and
the email address in the message header are trivial to forge. If you want a
reliable originator information read the originating ISP's logs. This might
take routing IPX to a box that has no IP address and bypassing lots of
firewalls. The better spammers routinely forge both addresses and it takes at
most 2 minutes to figure out how to do it (just read RFC 821).

The only reliable information is Received: headers, provided you are smart
enough to ignore those included by the spammers to confuse you. This usually
not that difficult because spammers almost invariably get the format wrong.
Many spammers do not add any Received: headers.
-- 
Duncan (-:
"software industry, the: unique industry where selling substandard goods is
legal and you can charge extra for fixing the problems."



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