mail() don't working

[BigBang]

Hey guys! Just asking to help me with this problem. I googled this forum and many others in trying to fix this, but without any result. I know. there are many similar topics, but any method didn't work. So, i'm not super guru, and i'm sorry about that
So, i have 2 dedicated server with many wordpress sites, based on cenos 6 and 7. Both have latest sentora install. Earlier, when sites was on shared hostings, wordpress sent to me emails with update info, new comments etc.
So, my ip didn't blacklisted, i've checked it.
When i'm trying to send some message from console like:

Code:

echo "This is the body of the email" | mail -s "This is the subject line" *******@gmail.com

I receiving that message:

Code:

send-mail: Cannot open mail:25

After checking mail log:

Code:

Aug  6 03:20:07 CentOS-74-64-minimal sSMTP[30564]: Unable to locate mail
Aug  6 03:20:07 CentOS-74-64-minimal sSMTP[30564]: Cannot open mail:25

Logically i have closed 25 port, buy i've added accept rules in iptables.

Tried add in "/etc/postfix/master.cf":

Code:

submission inet n - n - - smtpd

The last idea i had - closed port at hosting provider. So, i'm using Hetzner, and there are firewall with all open ports.

Any help will be appreciated. Thanks!