==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release):  1.3.1
- Deployed with iRedMail Easy or the downloadable installer?
- Linux/BSD distribution name and version: Ubuntu 18.04
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? No
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

Hi Guys,

I'm having problem sending email to domain.com with the below error:
From /var/log/maillog
"Warning: no MX host for domain.com has a valid address record"
From Iredmail 1.3.1 mailer-daemon:
"Host or domain name not found. Name service error
    for name=mail.domain.com type=AAAA: Host not found"

Here is the scenario:  iredmail 0.9.9 is currently working without any problem. What i did was, installed iredmail 1.3.1 into a new server using the same mail.domain.com as iredmail 0.9.9.

Note:
a. Able to send and received email to/from gmail.com, yahoo.com and hotmail.com
b. resolv.conf has a nameserver entry of our dns ip and google ip
c. /etc/postfix/main.cf "inet_protocols = all" "inet_interfaces = all"
d. Changed the inet_protocols to ipv4 and disabled ipv6 but still not sending mail to certain domain.

Any help is much appreciated.

Thanks,
JunG