On Tue, 2012-04-03 at 10:36 -0500, /dev/rob0 wrote: > > > > If you have a client connect from 1.2.3.4 and perform a host name > > lookup on that, so you get back host.example.com, would it impact > > on mail if a forward query for host.example.com returned multiple > > A records, say 1.2.3.4 & 5.6.7.8 alternating between the top of > > the result sets in a round robin? > > Multiple A records for a particular PTR value should not be a > problem. The order in which those records are returned cannot be > relied upon. If 192.0.2.22 connects to smtpd(8), and: > > 22.2.0.192.in-addr.arpa. PTR host.example.com. > host.example.com. A 192.0.2.2 > host.example.com. A 192.0.2.22 > host.example.com. A 192.0.2.222 > > Postfix would log the connection as host.example.com[192.0.2.22]. > "unknown[192.0.2.22]" is logged if: > > 1. 22.2.0.192.in-addr.arpa./PTR returns no value (including NXDOMAIN, > SERVFAIL, and NOERROR) > 2. Lookup of the 22.2.0.192.in-addr.arpa./PTR value does not return > an A record with 192.0.2.22 as value. > Thank you rob0, that clears it up nicely. Basically, as I understand it, if the connecting IP appears in a list of multiple A records for the host, it won't break.
I may have lost a Pizza, but I've gained useful knowledge. Kind thanks for your polite and very helpful reply. It is really appreciated.
