On Mon, 6 Jun 2005, Julian Mehnle wrote:
Where is this being verboten? I only use MX->CNAME (or MX->CNAME->CNAME)
because I believe it is technically valid. I would not be using it if I
believed it was verboten, so I'd really like to know.
http://www.faqs.org/rfcs/rfc1912.html
"Don't use CNAMEs in combination with RRs which point to other names
like MX, CNAME, PTR and NS. (PTR is an exception if you want to
implement classless in-addr delegation.) For example, this is
strongly discouraged:
podunk.xx. IN MX mailhost
mailhost IN CNAME mary
mary IN A 1.2.3.4
[RFC 1034] in section 3.6.2 says this should not be done, and [RFC 974]
explicitly states that MX records shall not point to an alias
defined by a CNAME.If you really want to do this, you can accomplish
the same thing by using a preprocessor such as m4 on your host files.
Also, having chained records such as CNAMEs pointing to CNAMEs may
make administration issues easier, but is known to tickle bugs in
some resolvers that fail to check loops correctly. As a result some
hosts may not be able to resolve such names"
--
William Leibzon
Elan Networks
william(_at_)elan(_dot_)net