FQDN Misery Re: To: Postfix, Mutt And No Root Mail? & amavisd-new Install

Derek Broughton news at pointerstop.ca
Thu Nov 8 14:10:51 UTC 2007

NoOp wrote:

> On 11/07/2007 10:43 AM, Leonard Chatagnier wrote:
>> As you see "hostnam and domainname" both give results
>> and nslookup indicates to me that
>> "ubuntu.gateway.2wire.net" is the FQDN for my Ubuntu
>> machine.
> No, it's not. For it to be an FQDN you need to add a . (dot) at the end
> of ubuntu.gateway.2wire.net; i.e., ubuntu.gateway.2wire.net(.)
> http://en.wikipedia.org/wiki/FQDN
Er, no.  It may be technically true but it _isn't_ what your system expects
and describes as an FQDN.  An FQDN is simply a domain name _containing_ a
dot, and ending with one of the recognized TLDs (Top Level Domain).

For instance:

# nslookup pointerstop.ca
# nslookup pointerstop.ca.

give exactly the same results.  However, 
# nslookup gateway.2wire.net.

returns NXDOMAIN

# nslookup gateway.2wire.net

tells me it doesn't exist _within_ my domain (but that's also just an option
within nslookup).  So, there's nothing technically wrong about using an
invalid domain as an FQDN in a mail server - but it _does_ need to resolve
on the host that's checking.  I do it all the time - my mail server
believes it's running at bella.pointerstop.ca, but you will never resolve
bella.pointerstop.ca from the outside world. However the MX for
pointerstop.ca always resolves - and I'm not sure if that makes a

> That said, if you want an actual DDNS that you can use as a proper FQDN
> for internet activity then go and get a free DDNS:
> http://www.dyndns.com/services/dns/dyndns/

That's certainly simplest.

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