Marc Perkel wrote: > Doing a reverse lookup on a misconfigured host and I get this result > from dnsstuff.com > > *Preparation*: > The reverse DNS entry for an IP is found by reversing the IP, adding it to > "in-addr.arpa", and looking up the PTR record. > So, the reverse DNS entry for 200.76.108.68 is found by looking up the PTR > record for > 68.108.76.200.in-addr.arpa. > All DNS requests start by asking the root servers, and they let us know what > to do next. > See How Reverse DNS Lookups Work <http://www.dnsstuff.com/info/revdns.htm> > for more information. > > *How I am searching*: > Asking e.root-servers.net for 68.108.76.200.in-addr.arpa PTR record: > e.root-servers.net says to go to ns2.dns.br. (zone: 200.in-addr.arpa.) > Asking ns2.dns.br. for 68.108.76.200.in-addr.arpa PTR record: > ns2.dns.br [200.19.119.99] says to go to B.NS.MX. (zone: > 76.200.in-addr.arpa.) > Asking B.NS.MX. for 68.108.76.200.in-addr.arpa PTR record: > b.ns.mx [200.23.179.1] says to go to dns6m.inext.net.mx. (zone: > 108.76.200.in-addr.arpa.) > Asking dns6m.inext.net.mx. for 68.108.76.200.in-addr.arpa PTR record: > Reports latam.rci.com. [from 200.76.111.202] > > *Answer*: > 200.76.108.68 PTR record: *latam.rci.com.* [TTL 86400s] [A=148.243.230.2] > **ERROR** A record for latam.rci.com. does not point back to original IP. > > > Exim see this as the sender_host_name being blank instead of returning > the misconfigured reverse lookup. Is there any way to just return the > reverse lookup even if it is misconfigured? > >
AFAIK, Exim already *does do* - THEN makes the comparison on what it receives and back-checks that. Might not be usr-visible, but the behaviour suggest such. But prefixes can pose a problem, especially where a correspondent uses broken or even 'stealth' outbound-only MTA's w/o proper DNS entries. KISS. $ host latam.rci.com latam.rci.com has address 148.243.230.2 $ host 148.243.230.2 2.230.243.148.in-addr.arpa domain name pointer latam.rci.com. Works fine. But ... $ host rci.com rci.com has address 198.151.36.111 $ host 198.151.36.111 Host 111.36.151.198.in-addr.arpa not found: 3(NXDOMAIN) Disagrees... Is that the cause? Bigger problem in that NetSol have been doing even worse for multiple thousands of parked/MX-only domains... Even the <domain>.<tld> do not agree, let alone prefixen. Bill -- ## List details at http://www.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://www.exim.org/eximwiki/
