External connections fail

[cinme]

I'm setup Zentyal on new computer, and open 993, 143, 25 ports on my mikrotik router, NAT also configured on router.
Next I add one mail user and setup The Bat mail client.
I use free ddns domain mydomainname.hldns.ru and have white IP.

When I try to connect from internal network to mail server - it work fine.
But when I try to set  server address as mydomainname.hldns.ru or IP then connection fails.
Rules on mikrotik work fine, ports open and NAT-ed (i have second win-server, it work fine).
What need to set in Zentyal to set connection work from internet?
Zentyal firewall - all rules is ALLOW for all ports.

[doncamilo]

 

https://www.arschkrebs.de/postfix/postfix_why_dyndns_does_not_work.shtml

Why do would someone like to config such a this mail system? 

Cheers!

[cinme]

https://www.arschkrebs.de/postfix/postfix_why_dyndns_does_not_work.shtml

Why do would someone like to config such a this mail system? 

Cheers!

Why external connections not work? In local network all work good.