Hello Comunity!

I have a question regarding the Webmin/iptables Firewall:
I tried opening port 25 on my machine, but it's only accepting connections from localhost.

see here:

root@Mailserver ~# telnet 127.0.0.1 25
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
220 domain.at ESMTP Postfix (Debian/GNU)
quit
221 2.0.0 Bye
Connection closed by foreign host.
root@Mailserver ~# telnet 192.168.16.174 25
Trying 192.168.16.174...
telnet: Unable to connect to remote host: Connection refused
root@Mailserver ~# iptables -L
Chain INPUT (policy DROP)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere
ACCEPT     icmp --  anywhere             anywhere             icmp echo-request
ACCEPT     all  --  anywhere             anywhere             state RELATED,ESTABLISHED
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:ssh
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:https
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:12320
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:12321
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:12322
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:smtp
ACCEPT     tcp  --  anywhere             anywhere             tcp
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:smtp

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

I also tried explicitly opening port 25, but no chance :/

What else can I do?

Thanks!!!