I've been following this tutorial : http://www.linuxmail.info/ to set a mail server on centOS 6. Everything was going fine until I reached this section : http://www.linuxmail.info/ . When I try and connect to my domain name via SMTP I get a connection refused but I've I use pop3 I connect to dovecot fine.
There are more official-ish docs on the CentOS wiki:
Probably a few others.
There could be a number of things that are wrong. One in particular is your ISP blocking port 25 traffic as an anti-spam measure. In that case, you should be using the SMTP submission port (587) for Postfix, or SMTPS (SSL-enabled SMTP) on port 465.
Verify that Postfix is listening to the public interface, e.g.,
If it's a SASL authentication issue, check your logs.
From the netstat output in the comments, it looks like Postfix is only listening to localhost.
Look at CentOS Wiki's Postfix configuration guide for the available options. In particular, you want to set