I’m trying to set up an email server. I can’t seem to get port 25 to open for me. I literally just did:
ufw disable
ufw reset
ufw default deny incoming
ufw default allow outgoing
sudo ufw allow 22/tcp
sudo ufw allow 25
sudo ufw enable
And then sudo ufw status verbose…
Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing), disabled (routed)
New profiles: skip
To Action From
-- ------ ----
22/tcp ALLOW IN Anywhere
25 ALLOW IN Anywhere
22/tcp (v6) ALLOW IN Anywhere (v6)
25 (v6) ALLOW IN Anywhere (v6)
However, one cursory glance of sudo netstat -tulpn | grep LISTEN and..
tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN 512/systemd-resolve
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 664/sshd: /usr/sbin
tcp6 0 0 :::22 :::* LISTEN 664/sshd: /usr/sbin
and telnet [my server IP] 25:
telnet: Unable to connect to remote host: Connection refused
What gives? How can I open up my ports?
UPDATE
At the advice of the users here, I decided to install Postfix now and check again if the ports are now being acknowledged..
sudo netstat -tulpn | grep LISTEN
tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN 512/systemd-resolve
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 664/sshd: /usr/sbin
tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 43246/master
tcp6 0 0 :::22 :::* LISTEN 664/sshd: /usr/sbin
tcp6 0 0 :::25 :::* LISTEN 43246/master
and
telnet [my server IP] 25
Trying [my server IP]...
Connected to [my server IP]
Escape character is '^]'.
220 ubuntu-s-1vcpu-1gb-lon1-01 ESMTP Postfix (Ubuntu)
It seems it's connected, but does that mean the port is open?
It appears as though you don't have an SMTP server listening on port 25. Start your mail daemon, and try again. (Also, SMTP never uses UDP, so you can change those '25' to '25/tcp' and it'll make your firewall more secure.)