Postfix misconfiguration or isp that closed port 25?

dev-null-devil · Tux's lil' helper Joined: 12 May 2003 Posts: 93

I don really know what's wrong with this, but i've set up postfix, configured it and according to faqs and online documentation, it's as it should be. However, when trying to send a mail to the server from my friends mailserver / yahoo etc, no mail arrives. I used netstat, just to check what ip it was listening to, and saw that postfix only listens on 127.0.0.1:25 and 192.168.51.1:25 (my local ip). But in the configuration file (main.cf), i specifically added my extern ip to listen to port 25.

I tried also to telnet to my server, on port 25 (Connection refused).
But now, the strange thing, i used nmap, to scan the server from another computer:
Results from another isp:
Port 25 (Filtered).
Results from another local computer (192.168.51.43):
Port 25 (Open).

So i dunno if my isp has closed that port? I thought nmap should display closed if my isp closed that port. Maybe some of you can help me while i'm screaming: Why god? Why??

taskara · Posted: Mon May 19, 2003 9:22 am Post subject:

I do think that most isp's close port 25, to stop your pc from being used as an smtp relay.

call them and ask! they can prob open it for you

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kopfarzt · Posted: Mon May 19, 2003 9:29 am Post subject:

According to your information (netstat), postfix is not listening to the external interface. That's on your side, and your ISP can do nothing about that.

But it's possible, that your ISP filters port 25. You can test this easily. Just install the package net-analyzer/netcat and let it listen to port 25 on your external interface: