justin wrote:
> hi,
> I have setup a mail server using postfix. I am behind a router
> which has its port 25 open. when i send a mail to my server using
> yahoo. Mailer daemon say cannot establish smtp connection (#4.4.1).
> Can any one it out its urgent.
> Thanks.
> justin....


Some basic troubleshooting steps are:

1. Make sure that Postfix is alive and semi-responding:
From a shell session on the same server that Postfix is running on, type: telnet 127.0.0.1 25
Make sure you get a welcome banner such as:
220 myhostname ESMTP Postfix (2.2.9) ready
Type in: helo world.com
Make sure Postfix responded and doesn't hang.
Type in: quit

2. Make sure that Postfix is listening on your IP address:

Run the command: $ netstat -an | grep :25
and make sure it's listening on 0.0.0.0 or your IP address, such as:
tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN

Repeat step #1 above, only using your IP address instead of 127.0.0.1

3. If possible, repeat Step #2 from another system that's on the same network subnet
as the Postfix server.

4. If possible, repeat step #2 from an system on the Internet (on the other side of your firewall).

5. Repeat step #4 using your system's name, instead of it's IP address.

6. See if your domains records are correct in external DNS by querying another's DNS service:
host mydomain.com cs.utexas.edu


--
Greg