Why is the port not visible?

Question

linux

Even I don’t understand I
put it, but it doesn’t work

Answer 1

Well, Lord, more information, the same thing all the time. Information from gulkin *uy.
What do you mean from outside?
1.For natom?
1.1 Are ports forwarded?
2. telnet to port 25 from outside - what does it give?

Answer 2

netstat -a | grep 25
And see how smtp is open