Hi thank you for your responses.
It uses the built-in mail server.
ufw is not active. I had checked that already.
$ sudo ufw status
Status: inactive
$
netstat is not installed on Ubuntu 22.04 LTS by default but ss is. The command I ran above:
sudo ss -tulpn | grep LISTEN
Re-running it still shows:
tcp LISTEN 0 4096 127.0.0.53%lo:53 0.0.0.0:* users:(("systemd-resolve",pid=603,fd=14))
tcp LISTEN 0 4096 127.0.0.1:52022 0.0.0.0:* users:(("jumpcloud-agent",pid=649,fd=24))
tcp LISTEN 0 512 0.0.0.0:443 0.0.0.0:* users:(("MailService",pid=653,fd=391))
tcp LISTEN 0 128 0.0.0.0:22 0.0.0.0:* users:(("sshd",pid=900,fd=3))
tcp LISTEN 0 512 0.0.0.0:80 0.0.0.0:* users:(("MailService",pid=653,fd=388))
tcp LISTEN 0 128 [::]:22 [::]:* users:(("sshd",pid=900,fd=4))SmarterMail is not listening on 443 for IPv6. I would expect to see a line with something like:
tcp LISTEN 0 512 [::]:443 [::]:* users:(("MailService",pid=653,fd=999))Is there a configuration file that tells "MailService" which interfaces (i.e. IP addresses) to listen on?