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Re: Help needed for my first mail server

Andrew McGlashan put forth on 3/15/2011 8:35 PM:
> Hi,
> Stan Hoeppner wrote:
>> MX records are for second level domains, thus you can't us an MX record
>> in this case as your system is a third level domain.  The MX records in
>> your case are for dyndns.org, your parent domain.
> Rubbish, you can have an MX at any level you like.

Andrew, you're not thinking in the context of the thread.  In response
to your out of thread thinking, sure, a DNS admin can create a fully
delegated sub zone to allow an MX for that sub zone.

What you've missed here is that the OP doesn't control his DNS.  He's
using the freebie DynDNS service, where there is no possibility of sub
zone delegation.  Therefore, to receive direct SMTP mail, he must use
the DynDNS paid service, another paid dynamic DNS service such as TZO,
or stick with free DynDNS and register his own domain as I suggested,
which is the cheapest solution, $5-20/year USD.

> What is important is that the MX record has a corresponding A record as
> well.

A static A record isn't required, and he has an A record already
provided by DynDNS.  If he registers his own domain, he'd simply have
the registrar create an MX record pointing to the DynDNS hostname name
assigned to him, such as:

              IN      MX 10  jason-hsu.dyndns-free.com.

The DNS server that hosts the SOA and MX for his domain isn't required
to also host the A record for the target of the MX entry, as long as an
A record exists for that FQDN on a DNS server somewhere on the net.

> Also, as has been mentioned already, it is highly advisable to have rDNS
>  {reverse DNS) -- without it, you should be using smart host, ie your
> ISP as an upstream sender.

Again, he's using DynDNS with a dynamic broadband IP.  He can't get
custom rDNS.  But this doesn't matter as he can setup relay via SMTP
auth to his ISPs relays.

> Using dynamic IP means that you can't properly run your own mail server
> for both sending and receiving directly.

Rubbish. ;)  There is no technical difference between a static IP and
dynamic WRT SMTP, thus one can "properly" run a mail server for both
sending and receiving directly.  The problem one runs into here, which
is probably what you meant to say, is merely receiver policy.  There are
few today that accept connections from PBL/DUL listed IPs, or those with
dynamic/generic rDNS.  Thus, use SASL auth to forward all outbound mail
through your ISP.


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