==== Required information ====
- iRedMail version (check /etc/iredmail-release):  0.9.7
- Linux/BSD distribution name and version: Centos &.4
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):  Mysql
- Web server (Apache or Nginx): Apache
- Manage mail accounts with iRedAdmin-Pro? None
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

System signature:
==============
1. Centos 7.4
2. MariaDB 5.5.56
3. Apache 2.4.8
4. PHP 7.1.12
5. IredMail 0.9.7

Assume my public main domain is “abc.com”, the public static IP is “123.123.123.123”.  Assume the email server internal static IP is “192.168.12.12” and its hostname is “mail.abc.com”. 

Port Forwarding on the Route/Gateway is used to manage the request mapping between the external static ip and the LAN servers.   

Port 25 of the public static IP is open.

Here is the MX DNS set up for the email server on my DNS registrar

Name    type        LLT        Priority           Data
=====  =======   ========     =========      ==============
@        MX         60       10             mail.abc.com               

I only have one public static IP which is already used for the web server on another machine.

So far I didn’t set up the A record. Not sure if it is necessary.

Since iRedMail is set up on a separate clean server on the same LAN, not sure if another public IP is needed for this VM to set up the ‘A’ record.

Plus, the Roundcube/SoGo webmail UI is intended to be open only to the Intranet. Employees need to VPN into the Intranet if they would like to access the webmail UI.

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So the current issue is that this email server can’t receive emails from the Internet, although it can send email out to an external email, like Gmail. Also, we tested and confirmed that the Intranet email sending and receiving work fine.

I don’t know if something is missed in configuration the DNS. Hope someone here could help.

Thanks!