At 12:42 24-02-2008, John C Klensin wrote:
The current sentence reads
"Such responses could, in principle, be covered by an SMTP
extension in the future."
Since there is a normative DNS prohibition on CNAME targets (in
RFC2181), that sentence is, strictly speaking, untrue. It could be
corrected by saying:
"Such responses could, in principle, be covered by DNS
changes or extensions and an SMTP extension in the future."
Or we could drop it. My instinct at the moment (i.e., I reserve
the right to change my
I suggest dropping that line as taking about DNS changes and SMTP
extensions makes the it convoluted. Suggested text is as follows:
When a domain name associated with an MX RR is looked up and
the associated data field obtained, the data field of that
response MUST contain a fully-qualified domain name. That
fully-qualified domain name, when queried, MUST return at
least one address record (e.g., A or AAAA RR) that gives the
IP address of the SMTP server to which the message should
be directed. Any other response, specifically including a
value that will return a CNAME record when queried, lies
outside the scope of this standard. The prohibition on CNAME
RRs is discussed in more detail in RFC 2181, Section 10.3 [29].
Regards,
-sm