Excuse me while I jump in on an old thread (yes, the vacation was
wonderful! :-).

[ On Wednesday, February 28, 2001 at 00:51:08 (-0700), Michael Milligan wrote: ]
> Subject: Re: Is postfix not searching PTR records correctly?
>
> This is absolutely rediculous in a mail context. Presumably, all these names
> are used on the right-hand side of an MX record, in which case, they could all
> be the *same* name, e.g., mail.isp.net and 207.254.115.105 only needs to
> reverse-map to mail.isp.net. The MTA should certainly be smart enough to
> handle virtual domains (e.g., userkingszone.com) internally. Postfix
> certainly can do it.

Such presumptions are not safe to make.

What if you take that list of A records displayed earlier and substitute
"www" for "mail" (and assume they all run SSL sites) and then add the
requirement that <userwww.example.com> is required to work? That's a
perfectly fine set of requirements and such configurations MUST work!

Indeed any ISP hoping to to offer countless e-mail-only domains with
unique looking A records (i.e. instead of using MX records for virtual
domains) then they'll eventually run into having arguments with ARIN
because they'll only be able to safely use a limited number of names
pointing to each IP address (limited by the size of the response for the
PTR record lookup), and thus eventually they'll eat up a bunch more IP
addresses than ARIN will permit. Not only that but it's rather silly
because anyone looking at the DNS to see if the domain is "virtual" or
not isn't going to be fooled anyway......

-- 
							Greg A. Woods
+1 416 218-0098      VE3TCP      <gwoodsacm.org>      <robohack!woods>
Planix, Inc. <woodsplanix.com>; Secrets of the Weird <woodsweird.com>

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