Networking error or bad System configuration.

Openbsd 7.0 at Vultr:

I have a new server at Vultr, everything was working correctly; except
mail rdns; e-mails were rejected by receiver.

The problem began because the ipv6 assigned was wrong ifconfig gave me a
different ip at the beginning and they did the change.

they changed the ipv6 to original and i configured the server with httpd,
smtpd, dovecot, dkimsign, icecast and ftp correctly, all them were
working.

They are insisting that the error is in the configuration system, and i
think that the error is because the IPs pass for another Vultr server that
is not configured for rdns.

Please, how might discover an error in the system or configuration? How to
identify it? and of course, how to repair it if it is in my hands?

# ifconfig vio0
vio0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
lladdr 56:00:03:a5:c6:15
index 1 priority 0 llprio 3
groups: egress
media: Ethernet autoselect
status: active
inet 8.9.36.198 netmask 0xffffff00 broadcast 8.9.36.255
inet6 fe80::5400:3ff:fea5:c615%vio0 prefixlen 64 scopeid 0x1
inet6 2001:19f0:5:f8c:5400:3ff:fea5:c615 prefixlen 64

# host agroena.org
;; connection timed out; no servers could be reached



# ping6 2001:19f0:5:f8c:5400:3ff:fea5:c615
PING 2001:19f0:5:f8c:5400:3ff:fea5:c615
(2001:19f0:5:f8c:5400:3ff:fea5:c615): 56 data bytes
64 bytes from 2001:19f0:5:f8c:5400:3ff:fea5:c615: icmp_seq=0 hlim=64
time=0.182 ms
64 bytes from 2001:19f0:5:f8c:5400:3ff:fea5:c615: icmp_seq=1 hlim=64
time=0.082 ms

# dig agroena.org

; <<>> dig 9.10.8-P1 <<>> agroena.org
;; global options: +cmd
;; connection timed out; no servers could be reached

# ping agroena.org
PING agroena.org (8.9.36.198): 56 data bytes
64 bytes from 8.9.36.198: icmp_seq=0 ttl=255 time=0.108 ms
64 bytes from 8.9.36.198: icmp_seq=1 ttl=255 time=0.054 ms
64 bytes from 8.9.36.198: icmp_seq=2 ttl=255 time=0.056 ms

I do not have idea, what files should i show you.

Thanks for your attention.

PD:
Actually i can access the server using ssh and console.