Reverse DNS question

[Janos Dohanics]

On Tue, 18 Feb 2014 15:43:24 -0800
Darren Pilgrim <list_freebsd at bluerosetech.com> wrote:

> On 2/18/2014 3:06 PM, Janos Dohanics wrote:
> > My Postfix logs show entries like this:
> >
> > Feb 18 08:35:13 barrida postfix/smtpd[86649]: connect from unknown
> > [207.238.171.17] Feb 18 08:35:13 barrida postfix/smtpd[86705]:
> > connect from spam2.continental-realestate.com[207.238.171.17]
> >
> [...]
> > # host 207.238.171.17
> > 17.171.238.207.in-addr.arpa domain name pointer
> > mail1.continental-realestate.com. 17.171.238.207.in-addr.arpa
> > domain name pointer mail.continental-realestate.com.
> > 17.171.238.207.in-addr.arpa domain name pointer
> > spam2.continental-realestate.com.
> 
> > 1. Other than network congestion, what might cause this recurring
> > name resolution failure?
> 
> There are a couple of issues with the above:
> 
> 1. More than one PTR record for a given IP address is a 
> misconfiguration.  It is supported and there is no RFC saying you
> must not have more than one, but in practice most software will only
> look for one and thus only take the first PTR RR returned from the
> query.

So, the 3 names are returned in a random order, and if the first name
returned does not resolve at all, or does not resolve to the smtpd
client's IP address, Postfix will log it "unknown"?

-- 
Janos Dohanics