server can't find IP address NXDOMAIN - email

Question

I am trying to set up SMTP mail on CentOS / WHM, so far without success. Each message gets frozen in the mail queue with the error '#Diagnostic-Code: smtp; 550-Sender has no A, AAAA, or MX DNS records.' The problem appears to be with my hostname.
I understand from other answers that I need to configure reverse DNS for SMTP to work, because the receiving mail server will reject mail if it comes from an IP without a reverse DNS - so I've added a reverse DNS zone for my hostname. But this has not helped (and don't see why having no reverse DNS would cause the 550 error I am getting anyway).
In named.conf:
controls {
inet 127.0.0.1 allow { localhost; } keys { "rndc-key"; };
};
options {
/* make named use port 53 for the source of all queries, to allow
* firewalls to block all ports except 53:
*/
// query-source port 53;
recursion no;
/* We no longer enable this by default as the dns posion exploit
has forced many providers to open up their firewalls a bit */
// Put files that named is allowed to write in the data/ directory:
directory "/var/named"; // the default
pid-file "/var/run/named/named.pid";
dump-file "data/cache_dump.db";
statistics-file "data/named_stats.txt";
/* memstatistics-file "data/named_mem_stats.txt"; */
allow-transfer { "none"; };
};
zone "whm.nantinet-c36.co.uk" {
type master;
file "/var/named/whm.nantinet-c36.co.uk.db";
};
zone "8.68.77.in-addr.arpa" {
type master;
file "/var/named/8.68.77.in-addr.arpa.db";
};
This is the zone file for nantinet-c36.co.uk:
whm.nantinet-c36.co.uk. 86400 IN SOA ns1.livedns.co.uk. my.email.co.uk. (
2017012706 ;Serial Number
3600 ;refresh
7200 ;retry
1209600 ;expire
86400 ;minimum
)
whm.nantinet-c36.co.uk. 86400 IN NS ns1.livedns.co.uk.
whm.nantinet-c36.co.uk. 86400 IN NS ns2.livedns.co.uk.
whm.nantinet-c36.co.uk. 14400 IN A 77.68.8.55
whm.nantinet-c36.co.uk. 14400 IN MX 0 whm.nantinet-c36.co.uk.
mail 14400 IN CNAME whm.nantinet-c36.co.uk.
www 14400 IN CNAME whm.nantinet-c36.co.uk.
ftp 14400 IN CNAME whm.nantinet-c36.co.uk.
This is the zone file for the reverse dns entry:
8.68.77.in-addr.arpa. 86400 IN SOA ns1.livedns.co.uk. my.email.co.uk. (
2017020204 ;Serial Number
3600 ;refresh
7200 ;retry
1209600 ;expire
86400 ;minimum
)
8.68.77.in-addr.arpa. 86400 IN NS ns1.livedns.co.uk.
8.68.77.in-addr.arpa. 86400 IN NS ns2.livedns.co.uk.
8.68.77.in-addr.arpa. 14400 IN A 77.68.8.55
8.68.77.in-addr.arpa. 14400 IN MX 0 8.68.77.in-addr.arpa.
8.68.77.in-addr.arpa. 14400 IN PTR nantinet-c36.co.uk.
8.68.77.in-addr.arpa. 14400 IN PTR whm.nantinet-c36.co.uk.
The nameservers work, I have an accessible web site running on the server. I am puzzled by this: if I dig +nssearch 8.68.77.in-addr.arpa, I get the error 'no servers could be reached'
Is there an error in my dns setup, or am I doing something else wrong here?
Thanks.

Answer 1

Yes, there is a problem with your DNS setup. The parent of whm.nantinet-c36.co.uk does not know about it, so it can't delegate to it, so nobody can look up any information about it. You can see a test of this here.