Re: CNAME records (was: Re: dynamic DNS within a non-dynamic domain)
On Tue, 10 Mar 1998, David Stern wrote:
> On Mon, 09 Mar 1998 20:23:06 CST, Rich Puhek wrote:
>> The MX record (Mail eXchange) is on your DNS server. It's what points
>> incoming mail for "<username>@foo.bar to the appropriate machine to handle
>> the mail. What's worked for me is the following:
>>
>> mail IN A 10.0.20.1
>> IN MX 10 mail
>>
>> It's probably not quite kosher (also note that these are my internal DNS
>> numbers), but it does work. I also have an 'A' record for 'debian' (the
>> name of our box, real imaginative) pointing to 10.0.20.1.
>
> Thanks. I get the jist of what's going on here. Further, I see Remco,
> who initiated this thread, has a static ip, and perhaps a
> semi-permanent net connection, so running his own DNS is perhaps
> feasible. I, OTOH, am running a dialup networking connection, and
> running my own DNS would not be practical (or so I've been told).
Yes, I have a static IP. It comes with a truly permanent connection. But
if the receiving end is doing the DNS lookup on my From: headers, it is of
no use to run my own DNS [1], since my DNS would not be 'authoritative'.
The university's DNS server is, of course, the authoritative one in this
case.
> This canonifying of hostnames sounded exactly like what was going on,
> so I read RFC-821.2 and this is entirely consistent with what seems to
> be happening:
> ------------------------------------------------------------------------
> Once the transmission channel is established, the SMTP-sender sends a
> MAIL command indicating the sender of the mail. If the SMTP-receiver
> can accept mail it responds with an OK reply. The SMTP-sender then
> sends a RCPT command identifying a recipient of the mail. If the
> SMTP-receiver can accept mail for that recipient it responds with an
> OK reply; if not, it responds with a reply rejecting that recipient
> (but not the whole mail transaction).
> ------------------------------------------------------------------------
I don't see how this justifies the DNS lookup. It just doesn't say it
shouldn't happen.
> However, this led me to wonder how I was able to send mail with bo for
> so long without problems. Initially, I thought my configuration must
> have changed, but recently I've realized that implementation of the
> latest anti-spam MTA features across the 'net roughly coincided with my
> hamm upgrade, thus it may not be my configuration that changed -- I'm
> not sure.
>
> At least this narrows the problem down to C_NAME lookup at my SMTP
> server send-time. Now all I have to figure out is how to alleviate
> that.
I don't know what your problem is, but my problem is purely cosmetical. If
my hostname is 'blaakmeer', I want that to be in the From: address of my
outgoing e-mail. Should I ever move to a different room, my IP would
change [2], the FQDN would change with it but the CNAME would 'move' with
me (i.e. it would point to my new IP). So, after I would have moved,
people could still send mail to ...@blaakmeer..., but everybody sending
mail to ...@cal011205... would have to be notified of the changed address.
Remco
[1] I do run my own DNS, but that is for cacheing purposes only.
[2] There is a one-to-one mapping between address and IP where I live. If
you behave badly, everybody knows where you live. The FQDN gives a very
good hint at that.
--
blaakmeer: 3:10am up 1:21, 7 users, load average: 2.99, 3.06, 2.93
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