[dns-operations] MX record definition?
Mark_Andrews at isc.org
Thu Dec 18 01:36:59 UTC 2008
In message <email@example.com>, Edward Lewis writes:
> That's the place for the definition.
> Don't know if there's a document that says why/that they are bad.
> I can only venture a guess - probably because the reason they are bad
> is weakly written application code that assumes the name in the MX
> record is a host name and not a domain name. (Host names in RFC
> 1123.) I.e., what do you get if you try to look up the A record for
Well the description pretty clearly says it it a host.
EXCHANGE A <domain-name> which specifies a host willing to act as
a mail exchange for the owner name.
Seeing a IP address in the exchange field of a MX record
in a master file is, almost always, a configuration error.
Seeing a IP address with a period at the end in the exchange
field of a MX record in a master file is also, almost always,
a configuration error
MTA that treat a "123.321.23.123." as a IP address are broken.
> As far as being a no-no: they aren't prohibited by the DNS
> specification. Perhaps there's a mail protocol restriction.
> At 15:21 -0800 12/17/08, Seth Mattinen wrote:
> >Does anyone know offhand where the MX record is defined? The best I
> >can find is section 3.3.9 in RFC 1035. I'm trying to find a
> >reference that says numeric MX records are bad. I'm assuming they're
> >a no-no, at least that's what I've always been told.
> >dns-operations mailing list
> >dns-operations at lists.dns-oarc.net
> Edward Lewis
> NeuStar You can leave a voice message at +1-571-434-5468
> Never confuse activity with progress. Activity pays more.
> dns-operations mailing list
> dns-operations at lists.dns-oarc.net
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: Mark_Andrews at isc.org
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