SmarterMail not receiving mails but can send out email

Well, set up my smartermail in new windows 2003 server. I've already make sure steps provided in Smartermail help file properly set.

WebMail URL (A Record) - Add an A or CNAME record for mail.example.com that points to the IP address of the webmail interface. This will allow users of that domain to access the webmail by typing in http://mail.example.com or http://mail.example.com:9998 in their web browser (depending on whether you use the included web server or IIS).

Mail Pointer (MX Record) - Add an MX record for example.com that points to the IP address that you assigned when adding the domain to SmarterMail. This will allow other email servers to locate your mail server.

Reverse DNS Record - Add a reverse DNS record for IP addresses assigned on the server to provide extra assurance to other mail servers. Also, it is recommended that the primary IP address of the server also have a reverse DNS record. Note: Adding reverse DNS may also require a change at your isp.

Also already setup iis to able login thru specific domain. Things work fine, able to send out email but not able to received email from external domain that not in the server. Strange, huh?

After check here and there, finally find out that we need to enable port in windows firewall.

Well, open my windows firewall and add in "Exceptions" to the port correctly. For my case, i just enable the port for below port

It's work. Hope can help.