Hi, Andy - A vague memory stirs…
Check the *Exim Specification* in the *String Expansions* chapter and see the text for the *$host_lookup_deferred* variable. There you'll read (emphasis mine): Looking up a host’s name from its IP address consists of more than just a single reverse lookup. *Exim checks that a forward lookup of at least one of the names it receives from a reverse lookup yields the original IP address. If this is not the case, Exim does not accept the looked up name(s)*, and $host_lookup_failed is set to “1”. Thus, being able to find a name from an IP address (for example, the existence of a PTR record in the DNS) is not sufficient on its own for the success of a host name lookup. If the reverse lookup succeeds, but there is a lookup problem such as a timeout when checking the result, the name is not accepted, and $host_lookup_deferred is set to “1”. See also $sender_host_name. Thank you for not obfuscating the IP address, by the way… It meant I could check both reverse and forward lookups for you, and find that although you have a reverse lookup: % nslookup 93.191.32.251 Server: 144.32.128.242 Address: 144.32.128.242#53 Non-authoritative answer: 251.32.191.93.in-addr.arpa name = asigra2.ldex.co.uk. Authoritative answers can be found from: 32.191.93.in-addr.arpa nameserver = ns1.pingnetworks.co.uk. 32.191.93.in-addr.arpa nameserver = ns2.pingnetworks.co.uk. ns1.pingnetworks.co.uk internet address = 93.191.32.131 ns2.pingnetworks.co.uk internet address = 93.191.32.146 you don't seem to have a forward lookup: % nslookup asigra2.ldex.co.uk Server: 144.32.128.242 Address: 144.32.128.242#53 ** server can't find asigra2.ldex.co.uk: NXDOMAIN So I'd guess this might be causing Exim to flag its reverse lookup as having failed? Cheers, Mike B-) On 10 June 2016 at 08:56, <[email protected]> wrote: > Hi, > > I'm running Exim 4.86.2 on FreeBSD 9.3 and I'm having an issue whereby > it is registered incoming mails as originating from hosts without an rDNS > record, but they do have an rDNS record. I've just enabled the > X-Host-Lookup-Failed ACL to add the extra header and it confirms what I was > seeing by enterpreting the "Recieved:" header. > > For example when sending from 93.191.32.251 I see: > > X-Host-Lookup-Failed: Reverse DNS lookup failed for 93.191.32.251 (failed) > > and > > Received: from [93.191.32.251] (port=49828 helo=asigra2.ldex.co.uk) > > > > but nslookup from the mail server itself provides: > > nslookup 93.191.32.251 > Server: 8.8.8.8 > Address: 8.8.8.8#53 > > Non-authoritative answer: > 251.32.191.93.in-addr.arpa name = asigra2.ldex.co.uk. > > > > Any clues as to why Exim is failing when nslookup/dig from the same host > using the same DNS server work? > > > > thanks in advance, Andy. > > > > > > > -- > ## List details at https://lists.exim.org/mailman/listinfo/exim-users > ## Exim details at http://www.exim.org/ > ## Please use the Wiki with this list - http://wiki.exim.org/ -- Systems Administrator & Change Manager IT Services, University of York, Heslington, York YO10 5DD, UK Tel: +44-(0)1904-323811 Web: www.york.ac.uk/it-services Disclaimer: www.york.ac.uk/docs/disclaimer/email.htm -- ## List details at https://lists.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://wiki.exim.org/
