JWM wrote:
Stefano,
The domain in question is: brandilyncollins.com
# host -t mx brandilyncollins.com
brandilyncollins.com mail is handled by 0 mxmail.register.com.
# host -t a mxmail.register.com.
mxmail.register.com is an alias for rcom-outblaze-com.mr.outblaze.com.
rcom-outblaze-com.mr.outblaze.com has address 205.158.62.41
rcom-outblaze-com.mr.outblaze.com has address 205.158.62.200
rcom-outblaze-com.mr.outblaze.com has address 205.158.62.206
rcom-outblaze-com.mr.outblaze.com has address 205.158.62.207
rcom-outblaze-com.mr.outblaze.com has address 205.158.62.229
rcom-outblaze-com.mr.outblaze.com has address 205.158.62.230
So, it is clear that the mx host name for brandilyncollins.com does not
have A or RR but instead it only provide a CNAME.
The specification is REALLY clear about this, you can see that they
provided a full paragraph to say that an hostname used as MX record must
NEVER be a CNAME (alias)
RFC2181 10.3: "Thus, if an alias is used as the value
of an NS or MX record, no address will be returned with the NS or MX
value.". If I understand correctly, supporting the CNAME for the MX
would be AGAINST the rfc.
So the problem is that RFC is extremely clear but Sendmail, postfix,
qmail, and exim, all support the aliased MXs.
We could consider to add this option to James, too, but don't expect to
happen soon.
"The Register" is not RFC compliant, so they are not providing a
compliant DNS service, and you should complain again.
I added an "improvement request" in our issue tracker to remember this
issue.
Stefano
-----------------------
here is the full 10.3 paragraph from rfc2181 (Clarifications to the DNS
Specification)
10.3. MX and NS records
The domain name used as the value of a NS resource record, or part of
the value of a MX resource record must not be an alias. Not only is
the specification clear on this point, but using an alias in either
of these positions neither works as well as might be hoped, nor well
fulfills the ambition that may have led to this approach. This
domain name must have as its value one or more address records.
Currently those will be A records, however in the future other record
types giving addressing information may be acceptable. It can also
have other RRs, but never a CNAME RR.
Searching for either NS or MX records causes "additional section
processing" in which address records associated with the value of the
record sought are appended to the answer. This helps avoid needless
extra queries that are easily anticipated when the first was made.
Additional section processing does not include CNAME records, let
alone the address records that may be associated with the canonical
name derived from the alias. Thus, if an alias is used as the value
of an NS or MX record, no address will be returned with the NS or MX
value. This can cause extra queries, and extra network burden, on
every query. It is trivial for the DNS administrator to avoid this
by resolving the alias and placing the canonical name directly in the
affected record just once when it is updated or installed. In some
particular hard cases the lack of the additional section address
records in the results of a NS lookup can cause the request to fail.
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