Double Irony! (was Re: [linux-elitists] ruben's stupid filter)

Dan Wilder dan@ssc.com
Mon Mar 25 09:40:55 PST 2002


On Mon, Mar 25, 2002 at 12:04:47PM -0500, Shawn McMahon wrote:
> begin  quoting what Dan Wilder said on Sun, Mar 24, 2002 at 05:58:58PM -0800:
> > 
> > If several large national or international ISPs started accepting 
> > email only from originating hosts with valid DNS, yes, there'd be
> > mass email failures, and things might clean up to the point where 
> > little guys like me could afford to entertain such an option.
> 
> Define what "broken" means in this context, please.
> 

I mentioned "valid DNS" which was meant in this context as shorthand 
for "valid DNS for HELO domain".

RFC1123:

      5.2.5  HELO Command: RFC-821 Section 3.5

         The sender-SMTP MUST ensure that the <domain> parameter in a
         HELO command is a valid principal host domain name for the
         client host.

Quoted previously in this thread.  <domain> refers to RFC822:

   3.5.  OPENING AND CLOSING

      At the time the transmission channel is opened there is an
      exchange to ensure that the hosts are communicating with the hosts
      they think they are.

      The following two commands are used in transmission channel
      opening and closing:

         HELO <SP> <domain> <CRLF>

         QUIT <CRLF>

      In the HELO command the host sending the command identifies
      itself; the command may be interpreted as saying "Hello, I am
      <domain>".


[ see also BNF definition for <domain> on pp. 30-31 of RFC822, from 
which I spare the eyes of the reader ]

The point pertained to RFC1123's requiring on the one hand a
valid principal host domain name, while on the other hand prohibiting
later in 5.2.5 the refusal of email from hosts not complying
with the requirement.

--
Dan Wilder





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