z9m9z.htt-consult.com is my mail server and receives emails from all over the world to port 25. Check that you are resolving to 50.253.254.3, as there once was a DNS secondary with old records from an old ISP, but I removed that server from the authoritative list a number of years ago...

z9m9z is running Redsleave6 on a CubieTruck using Postfix etal. It replacement CubieTruck with Centos7-armv7hl is 'almost' ready (see http://www.htt-consult.com/Centos7-mailserver.html for the setup; I am having SELinux issues). It handles 7-8K emails per day. it is accessed both externally and internally (by IMAP clients and SMTP from internal servers).

But if you look at the /var/log/maillog messages, Postfix did not even TRY to deliver the message to z9m9z. It made a decision that the mail was local, ignoring the domain in the TO: and dropped the mail into /var/spool/mail/rgm. So the challenge is on ClearOS to get it to recognize that it has to ship the mail out.

1) Do you mean the smtp server inside of ClearOS (my hostname is homebase.home.htt).
2) I do not want to run mail on homebase. It only is to deliver mail services like logwatch and cron generate ot z9m9z.
3) It is open. I recieve too much spam from all over the world for it not to be open