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Re: Last Call: draft-klensin-rfc2821bis

2008-03-25 19:33:55
On Tue, Mar 25, 2008 at 03:56:14PM +0100, Frank Ellermann wrote:
Bill Manning wrote:

FWIW, I'd like that...
Clarity can be established and interoperability _improved_ 
by limiting discovery to just A and MX records.  Perhaps a
note might be included that at some point in the future MX
records may become required.
Again, I have no problem with this approach if that's what
the consensus is.
...and that, too.  
so what is supposed to happen when I remove all "A" RR's from
my zones?

I'm not sure if we are talking about the same issue.  For SMTP
as it used to be since RFC 821 clients trying to find a server
accepting mail for x(_at_)y(_dot_)example look for y.example MX records,
and if they got something they locate corresponding servers
"by name" (A or AAAA), all details as explained in 2821bis.  

If they got nothing with their MX query RFC (2)821 and 2821bis
said that the client should try y.example directly "by name",
it could be an ordinary host with an SMTP server at port 25.

        right.  soa (

        ns foo.
        ns bar.
mailhost   aaaa  fe80::21a:92ff:fe99:2ab1

        is what i am using today.

the RFC's have the right idea.

For various reasons mentioned in this thread this "fallback"
or "implicit MX rule" isn't a good idea today, and some folks
like to get rid of it for AAAA.   RFC 2821 didn't say that
this is also supposed to work for IPv6, and therefore 2821bis
isn't forced to stick to it.

        its not a bad idea either, just that some folks
        are feeling grumpy. 
        RFC 2821 didn't say - and the presumption should be
        that since IPv6 is just like IPv4... then the IPv4
        methods shoudl work.

For the domain with only one SMTP host also almost nothing is
new, it is only encouraged (by the proposed note) to publish
this name in an MX record.

        what is being proposed is -FORCING- people to use
        an RR type they may not want to use.

You are not supposed to remove any A records from your zones.
You are not supposed to do anything at all, because you have
MX records as it should be... :-)

        er, NO.  SMTP has no dependence on what may or may
        not exist in the DNS.  Forcing SMTP to depend on DNS
        is a huge mistake.  And yes Virginia, I plan on removing
        A rr's from my zones (eventually)


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