Q:

Unable to Telnet into port 25 on CentOS PostFix Server

I'm trying to telnet into port 25 on a CentOS server that runs PostFix to test sending email messages from the server. 
When I try to telnet in from another CentOS box on the same network I get the message below:
 Unable to connect to remote host: Connection refused 
SELinux is disabled and I've opened port 25 in iptables...what else should I be looking at? 

A:

Run the following the check if postfix is listening on port 25/tcp:
netstat -plnt |grep :25
You should see a line like:
tcp        0      0 0.0.0.0:25                  0.0.0.0:*                   LISTEN      2460/master
If you don't see such a line, check /etc/postfix/master.cf. 
In that file, you should see a line like:
smtp      inet  n       -       n       -       -       smtpd

The first column is the port, which postfix derives from /etc/services. 
You should look up general documentation on setting up Postfix, so your server doesn't become a spam relay.   The CentOS wiki has fairly good documentation in that regard. 
Update:
Also, look at http://www.postfix.org/postconf.5.html#inet_interfaces which will describe how to configure Postfix to listen on different network interfaces.   The relevant line will be found in /etc/postfix/main.cf. 

A:

I edited the file /etc/postfix/main.cf.   The parameter to look up was  

inet_interfaces = localhost

I changed it to

inet_interfaces = $myhostname, localhost

Restart postfix.    The problem was fixed. 

A:

I had this problem and found that I needed to do:
# service postfix stop

followed (a bit later) by
# service postfix start

Postfix reload did not seem to close and then re-open the required ports.