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

Dan Wilder dan@ssc.com
Mon Mar 25 08:20:57 PST 2002


On Mon, Mar 25, 2002 at 08:08:57AM -0800, Rick Moen wrote:
> Quoting Dan Wilder (dan@ssc.com):
> 
> > Ah, dang.  I knew you'd ask me that.  Lemmeesee ... mumble mumble ...
> > ahh, here it is.  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.  As a result, the receiver-SMTP will not have to
> >          perform MX resolution on this name in order to validate the
> >          HELO parameter.
> > 
> >          The HELO receiver MAY verify that the HELO parameter really
> >          corresponds to the IP address of the sender.  However, the
> >          receiver MUST NOT refuse to accept a message, even if the
> >          sender's HELO command fails verification.
> > 
> > 
> > No doubt there's good reason.   It likes me not.  That guy MUST do
> > this, but you MUST NOT insist on it.   A standard without a
> > consequence.
> 
> The "good reason" may have been merely that some large site du jour
> was expected to dig in heels and say "No, we don't intend to fix our
> broken HELO support any time soon.  Have a nice day."  The rationale
> may have been nothing more lasting than that.

Unfortunately there are several large sites du jour whose HELO
contains something not remotely plausible.  So you can't ignore
RFC1123 5.2.5 without cutting off email from some big chunks
of the net.

I'm stupid enough to have tried it.  Fortunately I watched a tail -f
on the mail log.  Several minutes later I turned it off and began 
sending apologies.

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 Dan Wilder <dan@ssc.com>   Technical Manager & Editor
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