[ On Wednesday, March 27, 2002 at 11:47:56 (-0500), Jeff Mcadams wrote: ]
> Subject: Re: [Exim] Exim 4.02 new "feature"
>
> I have mixed feelings...practically speaking, as a business, rejecting
> underscores (in particular) is a sure recipe for business suicide for an
> ISP.
(Un)Fortunately ISPs are in the ideal position to make the biggest
difference and to make it quickly and make it stick....
> On yet another hand, though (three hands?), standards are all about
> supporting interoperability. Thus the "Be liberal in what you accept,
> and conservative in what you send" concept. Allowing underscores
> enhances interoperability in almost all cases, and given that the HELO
> hostname is really (practically) not used for anything, then accepting
> underscores really does no practical harm.
That's the most mis-understood and most frequently mis-applied "concept"
in the entire history of the Internet. That's advice for protocol
designers, not for sysadmins!
The problem with underscores in hostnames has to do with the fact that
by allowing them you are actually hindering interoperability. There are
still many hosts which interact with Internet e-mail and which cannot
handle underscores in hostnames. By allowing underscores at the
beginning you may allow an e-mail to be generated and transmitted which
cannot ultimately be received at its final destination. So in the
interests of interoperability you have to prevent the underscores
immediately.
(indeed the BIND-9 implementors having turned their backs on this issue
are not helping much either)
--
Greg A. Woods
+1 416 218-0098; <gwoods@???>; <g.a.woods@???>; <woods@???>
Planix, Inc. <woods@???>; VE3TCP; Secrets of the Weird <woods@???>
