[OT] RE: How important is static IP? NOW: MX Records

["Paul Gordon" <paul_gordon@xxxxxxx>]

Mark,

I don't _believe_ this is correct according to RFC974...

Here's a couple extracts from that document...

  "If the response does not contain an error response, and does
not
   contain aliases, its answer section should be a (possibly
zero
   length) list of MX RRs for domain name REMOTE (or REMOTE's
true
   domain name if REMOTE was a alias).  The next section
describes how
   this list is interpreted"


Thus it is a valid response for a resolver to return zero MX records for a
domain in response to a query..

Additionally...

  "It is possible that the list of MXs in the response to the
query will
   be empty.  This is a special case.  If the list is
empty, mailers
   should treat it as if it contained one RR, an MX RR with a
preference
   value of 0, and a host name of REMOTE.  (I.e., REMOTE is
its only
   MX).  In addition, the mailer should do no further
processing on the
   list, but should attempt to deliver the message to
REMOTE.  The idea
   here is that if a domain fails to advertise any information
about a
   particular name we will give it the benefit of the doubt and
attempt
   delivery."


Thus, according the the RFC, a mailer *should* attempt delivery to a domain
that has no MX records using just the domain name, and whatever that 
resolves to. (So like I said, if the SMTP server is on the IP address that
the domain name resolves to, no MX record is required).

Of course, it may well be that this has subsequently been superceded by
another RFC which may contradict this, but I'm not aware of that being the
case. Additionally I suppose it may well be that certain mailers don't 
implement this feature, but again, I've not come across any
personally...

One more thing to add I guess is that no-one is suggesting that this is a
"good thing" to do... I'm just saying that it's possible. In a
simple 
home-user environment, it's possibly best not to bother with MX records, as
it is quite easy to **ck things up and send email off to the wrong
place!

Paul G.


>From: "Mark Harrison" <Mark.Harrison@xxxxxxx>
>Reply-To: ukha_d@xxxxxxx
>To: <ukha_d@xxxxxxx>
>Subject: RE: [ukha_d] How important is static IP?
>Date: Wed, 29 May 2002 10:18:46 +0100
>
>You _do_ need an MX record for sending mail to a Domain.
>
>Let me explain, however, why, AIUI, Paul doesn't.
>
>The Domain in this case is HOMEIP.NET - it has an MX record properly
>defined, as mail.dyndns.org (priority 20) and mail2.dyndns.org
(priority 
>50.)
>
>To send email to the SubDomain paulgordon.homeip.net you first send
email 
>to the domain (homeip.net's mail server). Homeip.net's mail server runs
a 
>specially modified routing algorithm to allow it to send mail to
wherever 
>the SOA is defined on any of its subdomains.
>
>
>What this means in practice is that, if you want to host something
dynamic, 
>then you don't need to set up your own MX record - the dynamic domain
>provider will sort this for you.
>
>If you want to host a real domain, for example foxybanana.com, you need
an 
>MX record.
>
>
>      -----Original Message-----
>      From: Paul Gordon
[mailto:paul_gordon@xxxxxxx]
>      Sent: Tue 28/05/2002 21:49
>      To: ukha_d@xxxxxxx;
wendyjaynegordon@xxxxxxx
>      Cc:
>      Subject: RE: [ukha_d] How important is
static IP?
>
>
>
>      Personally, I don't generally find
having dynamic IP a problem for home 
>use.
>
>      As previously mentioned, just about the
only thing I can't get it to do is
>      to host a provate domain. - It's usually
tied to the namespace that the 
>DDNS
>      provider owns, so for instance,
DynDNS,org have about 20 domain trees that
>      you can choose to be under, hence I have
Paulgordon.homeip.net, but I 
>can't
>      have gordon-net.co.uk which I also own
(but am about to allow to lapse...)
>
>      a couple of small points to bear in
mind:
>
>      1: - you *CAN* have an SMTP feed to a
dynamic IP address - I have one
>      working perfectly, - mail to
paul@xxxxxxx to see it in
>      action... :-)
>
>      2: - you do *NOT* _need_ an MX record at
all to receive mail, - you only
>      need an MX record if your SMTP listening
server is on a different IP 
>address
>      to that which your DNS "A"
record resolves... - Do an NSLOOKUP on
>      paulgordon.homeip.net, you will see it
resolves to 80.1.127.35 - as my 
>SMTP
>      mail server is listening to port 25 on
that IP, I do NOT have (or need) an
>      MX record configured.
>
>      HTH
>
>      Paul G.
>
>
>
>      >From: "Chris Bond"
<chris@xxxxxxx>
>      >Reply-To: ukha_d@xxxxxxx
>      >To: <ukha_d@xxxxxxx>
>      >Subject: RE: [ukha_d] How important
is static IP?
>      >Date: Tue, 28 May 2002 13:27:09
+0100
>      >
>      > > It seems a few of us are
trying to decide which ADLS ISP to go with
>      > > at the moment, so I'd like to
know just how important those who've
>      > > already taken the plunge feel
it is to have static IP?
>      >
>      >Well if you want to use SMTP mail
its very important and it's the best
>      >mail method to use, don't need to
mess with pop3/imap :)
>      >
>      > > Which HA toys might need
static now or in the near future?
>      >
>      >Lots :)
>      >
>      > > I presume if I want to run a
mail server I need static for my DNS MX
>      > > record to point to. Is this
correct, or could you get away with
>      > > something like dyndns? My
guess is that dyndns would sometimes be out
>      > > of date and mail would get
bounced.
>      >
>      >I'd stay away from dyndns for SMTP
mail, there are a few people that
>      >offer backup mx but at the price you
pay u might as well get a static
>      >ip.
>      >
>      >Eclipse charge 26quid all inc for
Adsl with 5 static ips :)
>      >http://www.eclipse.net.uk.
>      >
>      >Kind Regards,
>      >Chris Bond
>      >
>
>
>
>
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