I can receive, but not send email.

[republicus]

Code:

587/tcp   open     submission

Are you sure you haven't configured postfix to submit only over port 587?

Check your postfix configuration has:
[/etc/sentora/configs/postfix/master.cf]

Code:

smtp      inet  n       -       n       -       -       smtpd

smtp service type is likely the first line of services

If you add the service, restart postfix and try again.

If that doesnt resolve your issue, I also noticed the domain you provided, vestraweb.com, is refusing to connect at port 80/443 for login or www subdomains. Are you sure you have your gateway/firewall configured properly?

Try stopping the iptables/apparmour service and restarting postfix/dovecot to rule out firewall issues.

Use telnet to check

Code:

telnet localhost 25

Try using ports 25 and 587; replacing localhost with your server IP and public IP
If telnet responds without error then the port is open and responding.