CWP7 SMTP NOT WORKING

I have a freshly installed CWP7 panel with Centos 8. Email account is setup, I can receive and send mail in Roundcube.
Now, configured my Thunderbird client for the mail server. I can receive POP3 emails but cannot send email in SMTP protocol thru Thunderbird. it says:

"The message could not be sent because the connection to SMTP server smtp.xxxx.net  timed out"

What is wrong?

Thanks

Your mail clients tries to connect from outside your network which is absolutely correct.

Without opening the Ports on your router, you won't be able to connect to your server from outside.

I use the smtp server of hostgator   with Thunderbird client, works fine  (ISP  Rogers Canada)  how does that work?