> On Sep 10, 2019, at 4:41 PM, Bill Cole > <postfixlists-070...@billmail.scconsult.com> wrote: > >> Hello, >> >> I have a question regarding DNSBL usage with the main.cf >> smtpd_client_restrictions parameter. >> >> I have a server configured to check SpamHaus: >> >> main.cf >> . . . >> smtpd_client_restrictions = reject_rbl_client >> zen.spamhaus.org=127.0.0.[2..11], >> . . . >> >> This has been working very well, although I noticed the following error in >> my syslog: >> >> Sep 7 16:13:08 server postfix/smtpd[28363]: warning: >> 188.50.102.94.zen.spamhaus.org: RBL lookup error: Host or domain name not >> found. Name service error for name=188.50.102.94.zen.spamhaus.org type=A: >> Host not found, try again > > A common cause of this is is if your DNS resolver thinks that you have IPv6 > connectivity (e.g. because you have an autoconfigured interface or a VPN with > an IPv6 address) but you really do not. The extensive collection of DNS > servers handling the zen.spamhaus.org <http://zen.spamhaus.org/> zone > includes many names that have as many AAAA records as they do A records and > if your resolvers tries one of those, you get a message as above.
Hi Bill, Thanks for your reply. Interesting. In this case, the DNS resolver I use is one that I run on the mailserver itself, which has IPv4/IPv6 connectivity. I know this host can successfully access both as we send and receive Gmail mostly over IPv6 whereas most other traffic is delivered over IPv4. With the SMTP traffic handling both ok I would assume that my DNS resolver is also ok (I haven’t made any configuration changes to Bind to make it prefer IPv4 or IPv6 when it performs recursive lookups) ? Thanks, - J
