Re: [cobalt-users] MX record question / Raq4i

[flash22@xxxxxxx]

On Tue, 18 Dec 2001, BT wrote:
> > >>  domain.com.      IN      MX      30      domain.com.
> > >>  mail.domain.com. IN      MX      30      domain.com.
> > >>  www.domain.com   IN      MX      30      domain.com.
> > >>
> 
> so what's wrong with three A records for mail. ftp. www. and one MX for
> mail.???

Nothing, provided all your mail is addressed to user@xxxxxxxxxxxxxxx and
you don't get anything addressed to user@xxxxxxxxxx ;P

And assuming mail.domain.com is what your IP address reverses to if you
also want to be compliant with the requirement that your mail server
accept IP routed mail ...(Otherwise you are forcing it to act in a way
that makes it violate the specified MX routes)

Some folks do in fact use configurations like this, providing no A
(IP) record for the base domain, and requiring all the services to access
only deeper domains...Why is a bit  involved ;P

The www.domain.com entry seems to be a requirement of the way sendmail is
configured on Raq's , it's a bit silly from an external point of view, but
the machine needs it internally so it can authoratively handle the
*@domain route properly

The authority document is RFC1033

  "MX records specify where mail for a domain name should be delivered."

Note that it says 'domain name' , not just 'domain', The RFC's tend to
have very precise language, most of the time, usually, generally ;)


Other obscure trivia, for folks using CNAMES for web aliases

RFC974 requires resoloution of CNAMES *before* MX lookups (client)

Apparently, this was worded too obscurely, as
RFC1480 went to the trouble to specificly prohibit MX -> CNAME-RR 

  "It is not appropriate to ask to MX "your-host" to "path-host" (this
   is sometimes called double MXing).  The host on the right hand side
   of an MX entry must be a host on the Internet with an IP address"


gsh