I've encountered this failure in a different context. This machine uses a PCMCIA ethernet card for connectivity. Postfix is configured as a satellite system. After several weeks running during which time I reconfigured eth0 to use a static ip address rather than dhcp, resolvconf presented me with a null /etc/resolv.conf on rebooting. Correcting the file and restarting networking did not solve the problem although don't think I restarted postfix. Perhaps postfix shouldn't remember the dns setup independantly of the OS. I am not on good terms with resolvconf.
The MX record for my isp, clear.net.nz, points to mx.clear.net.nz while they advertise their smtp server as smtp.clear.net.nz which is set as relayhost in postfix. There is no MX record listed for smtp.clear.net.nz or mx.clear.net.nz. ... (delivery temporarily suspended: Host or domain name not found. Name service error for name=smtp.clear.net.nz type=MX: Host not found, try again) /etc/network/interfaces had 'auto eth0' at the end of the file rather than before the eth0 stanza so I moved that to it's traditional location and added 'allow-hotplug eth0' as well before reloading networking, hoping that this would improve detection of the pcmcia card on boot. On restarting postfix mail delivery resumed. Some of these things are likely red herrings and the aetiology of my experience may not be the same as that of the original reporter. There are no IPV6 routers present. Further analysis delayed due to lack of sleep. -- Can't deliver mail through mixed IPv4/IPv6 smarthost https://launchpad.net/bugs/12937 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
