CNAME records having MX

[Joseph S D Yao]

On Fri, Dec 14, 2001 at 03:10:03PM -0800, glen herrmannsfeldt wrote:
> You could say a little more than 'nope'.
> 
> I only have an older version of "DNS & BIND" here, which doesn't say
> anything about this.  
> 
> There is a long and complicated history on problems with MX pointing
> to CNAME's, resulting in that now being illegal.  That one has
> to do with mailers knowing when to forward mail and when to accept
> it, and doing it wrong.
> 
> If there is a new reason that didn't exist in older versions
> of BIND you might tell me, and other list readers, what it is.

I'm sorry, I answered this fully weeks ago when the question was asked.
It may be archived somewhere.  Basically, from RFC2181, if you have

	xxx	IN MX	10 yyy

then #10.1 forbids xxx from being an alias, and #10.3 forbids yyy from
being an alias.  An alias is the LHS (label) of a CNAME record.

RFC2181 is useful, because it brings together information from several
previous RFCs to help explain and prevent several prevalent types of
bad behavior in DNS.

I hope this helps.

Bookpool (www.bookpool.com) may still have their 40% off sale on 4th
edition DNS & BIND.

-- 
Joe Yao				jsdy at center.osis.gov - Joseph S. D. Yao
OSIS Center Systems Support					EMT-B
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